Undoubtedly traffic congestion continues to be a challenge that negatively impacts socio-economic activities in most cities in the world. It does not only hinder the smooth movement of people but also freight and services. Admittedly, there have been a number of studies that have examined the causes and effects of traffic congestion in Ghanaian cities; nonetheless, these studies have largely concentrated on the larger metropolis which includes Accra and Kumasi with little attention given to mid-sized emerging urban centers. Using data collected from field survey, in-depth interviews and field observations in Sekondi-Takoradi, this study examines the effects of traffic congestion on socio-economic activities along five major road corridors in the study area. The survey data were analyzed using descriptive and inferential statistics while in-depth interviews were integrated with the results using quotes from informants. The findings from the study revealed a spatial variation of the effects of traffic congestion along the five corridors studied. In particular, it was observed that increased traffic congestion led to the reduction in sales made by traders and commercial drivers, while students and workers who used these roads also asserted they often get to school and workplaces very late. The study therefore recommends road expansion along these routes and use of road tolls to regulate the activities of ‘trotro’ (public buses) and taxis in the city in order to minimize traffic congestion in the city.
Traffic congestion is a worrisome situation for most dwellers in cities across the world. In view of the constraints associated with traffic congestion, an effort has been made through scholarship to understand the traffic congestion with the intention of providing appropriate remedies for this problem (Porter and Abane, 2008). Undoubtedly, major factors that have contributed to vehicular traffic worldwide have been the rapid growth of cities, mostly in an unplanned fashion and also the increase in automobile vehicles (European Conference of Ministers of Transport (ECMT), 2007). Notwithstanding efforts made by city planners in their attempt to finding lasting solutions to the problem of vehicular traffic, such planners cannot avoid the continuous modeling of efficient ways of providing the urban centre with the needed transport services since transport is the daily rhythm of life (Hoyle, 1988). In particular, traffic engineers, transportation planners and public officials responsible for metropolitan transportation systems are frequently criticized for failing to make an improvement in traffic congestion (Taylor, 2003; Victorian Competition and Efficiency Commission (VCEC), 2006).
According to Adenle (1981), the causes of vehicular traffic congestion in urban areas include the increased pace of growth of the population and expansion of urban settlements. The former is normally occasioned by regional inequalities in development which often drive human migration to the urban areas in search of employment opportunities in commerce, construction, and manufacturing. The inevitable outcome of this process results in pressure on the existing transport system in urban areas (Osoba, 2012), while the concentration of people and activities also seriously hampers the free flow of vehicles along main road corridors (Osoba, 2012).
The case of a country like Ghana becomes more pronounced as traders who ply their trade in cities refuse to abide by laws that restrict them from the use of the edges of roads as places of petty trading (Ministry of Road and Highways, 2010). This is a major characteristic of the Central Business Districts (CBD) in major cities in the country and Sekondi-Takoradi is no exception. Sekondi-Takoradi metropolis has experienced rapid growth over the years, with a current population size of 559,548, making it the third largest city in Ghana (Ghana Statistical Service (GSS, 2012a, b; Grants and Yankson, 2003). The traffic situation in the metropolis seems to be on the increase, and it is suggested that if the current trend goes unabated, it will be archetypal to that of Accra and Kumasi (Ministry of Energy and Petroleum, 2014).
Presently, Takoradi is faced with undesired traffic congestion due to the lack of efficient spatial planning and forecasting of the City’s growth and performance (GNA, 2012). This is particularly true for most cities in Ghana, notably Accra and Kumasi, due to the failure by governments to implement policies and programmes to mitigate urban traffic congestion (Addo, 2006, p.5). Furthermore, the Department of Urban Roads (2012, cited in a report by the STMA (2013 p.44) stated that Takoradi over the years has experienced tremendous increase in the volume of road traffic especially in the CBD. For instance, in their study of ‘Vehicular Traffic in Sekondi-Takoradi’ on some selected arterial roads in Takoradi, Mahama (2012) found that road traffic in Takoradi generally experienced a positive growth rate of 1.51% between the years 2003 and 2008.
Again, according to the Ministry of Energy and Petroleum (2014), other factors that cause traffic congestion in the city include competition among different services that depend solely on the road transport services in the city. Such services comprise catering, hospitality, logistics supplies, freight forwarding, fabrication and waste management services (Adams et al, 2014). Owing to the increase in traffic congestion, socio-economic activities within the city are negatively affected, resulting in a decrease in total economic output of the city (Sekondi- Takoradi Medium Development Plan (STMDP, 2011).
Since mobility is such a vital part of enhancing economic growth, it is important that we address constraints within the transport system in Takoradi, especially in light of its recent rapid growth. In particular, there is an urgent need to understand the consequential effects of vehicular traffic on socio-economic activities in the city. This study seeks to investigate the relationship between traffic congestion and socio-economic activities in Takoradi. The theory of Spatial Interaction as espoused by Ullman in the 1980s is used as the theoretical framework guiding this study. Our choice of the theory of spatial interaction emanates from the fact that in order to understand the interconnectedness between traffic congestion and socio-economic activities in the Central Business District (CBD) of Takoradi, there is a need to understand the causes, sources and direction of the flow of traffic in the city.
Situation of traffic congestion in Ghana
The vehicular population ratio in Ghana grew steadily from 31 vehicles per 1,000 population in 2002, to about 44 vehicles per 1,000 population in 2008 (Addison, 2012). Addison (2012) also estimated that Accra has the highest number of registered vehicles of 605,739 followed by Tema 256,956 and Kumasi 200,116 as of March 2012. The total number of registered vehicles in Ghana as of March 2012 stood at approximately 1,425,900. In the year 2013, however, the number of vehicles on roads in the country increased by nearly 23 percent between January and December (Ministry of Transport, 2014).
Unfortunately, the expenditure of the Government of Ghana to expand and build more roads to accommodate the increase in vehicle importations went down by GH¢200million in 2013 (GSS, 2012). In 2014, the number of vehicles registered by the Driver and Vehicle Licensing Authority (DVLA) was 174,234, which was 22.86% higher than the previous year’s figure. At the same time, the DVLA inspected about 946,284 vehicles for road-worthiness in 2014, which brings the total vehicle population in the country to nearly a million, with concentration again in the two biggest cities, Accra and Kumasi (GSS, 2012). With this increased number of vehicles in the country coupled with increased population, poor planning of our cities and road infrastructure, poor traffic management, the nature of the public transport system force people to depend on private vehicles, hence increasing the traffic. Thus, the point should be made that congestion is a systemic problem and all angles need to be looked at (Ministry of Transport MoT, 2012).
Case of Takoradi
Takoradi being the largest and most vibrant city in the Western Region of Ghana benefitted enormously from the establishment of a harbour in 1948 (Obeng-Odoom, 2014) and the development of the railway line connecting the city to the interior part of the country. The railway system, once constructed, enjoyed considerable support from Ghana’s first president, Dr Kwame Nkrumah, after Ghana gained independence (1957-1966). However, the railway sector saw some decline during the 1970s (Tsey, 2013) and vehicular transportation took over as the major means of transport in the country and also in Takoradi. The problem relating to the decline of the railway sector is attributable to a number of factors. These include inadequate investment in the sector, inefficient management and competition from the road sector (Tsey, 2013).
Furthermore, according to Obeng-Odoom (2014: 428) ‘‘the political elite oversaw an overt, systematic program to reduce the vibrancy of the rail sector, following a series of railway worker strikes’’. As the sector became a nuisance to successive governments, it no longer attracted sufficient central government support. The 1980s witnessed a new approach to Ghana’s economic development problems, identifying state-led management of the economy as an inefficient strategy and the bane of Ghana’s problem and hence the need to adopt private sector management to enhance economic vitality. Unfortunately, the expectation that investment in the railway sector will revitalize the sector did not materialize.
Vehicular transportation on the other hand was seen by the managers of the economy as a more viable transport mode and symbol of modernity (Addo, 2006). The first road was completed in 1895 and the first car arrived in 1902 (Ministry of Roads and Highways, 2014). Today, most goods such as manganese and bauxite which used to be transported by rail are now transported by road and the situation is putting pressure on the already fragile roads, besides the increased accidents involving vehicles (Ghana News Agency, 2012; Asomaning, 2010). Obeng-Odoom (2014)) stated that the return on newly constructed roads which was 29% was far higher than rail (20%). As a result, the World Bank recommended that the management of rail should be left to market forces, with support to road construction and maintenance done by government (Obeng-Odoom, 2014).
The streets in the city of Takoradi are quite old, and only functioned optimally back in the 19th century. Other factors that account for the worsening traffic situation in Takoradi, according to Armah (2012), cited in a Ghana News Agency (2012), include ‘‘the oil find, which is attracting several people to the city, the presence of the harbour which serves as a transit for the export and import of goods [as well as a market-place for the] services rendered by the banks, traders, manufacturing and construction firms and finally transport terminals such as Accra and Takoradi Stations’’.
Socio-economic effects of traffic congestion
As indicated the paper could not have exhausted all the forms of socio-economic issues that can be or are influenced by traffic congestion. As a result, the following activities were exmanined:
Work
Traffic congestion affects work in many ways. A typical example is labour productivity since productivity deals with the ratio of volume measure of output to the volume measure of input and input of labour. This is further directly related to the supply of labour (OECD, 2006), implying that traffic congestion reduces man hours needed to work and further reduce the ability of labour to provide optimum input to yield an equal output. Nadiri and Mamuneas (1996) and Takyi et al. (2013) argue that productivity is an investment by a state in transportation while output is the gross domestic product (GDP). For instance, a study by Metro Denver Economic Corporation showed that in Metro Denver, Mountain Resort Region, Colorado, a 0.5% decrease in man’s productivity due to congestion resulted in a $728 million decrease in national GDP (Development Research Partners, 2007). A state that invests efficiently in transportation will therefore ensure an adequate supply of labour.
Furthermore, road traffic congestion affects the ease to distribute goods and services within the city. In other words, congestion impairs people’s free movement and therefore affects a wide range of activities such as the distribution of goods and services and market opportunities in the cities, which can best be delivered through transport mobility (May and Marsden, 2011). Congestion further reduces productivity through increased inventory holding by manufacturers and retailers as a result of unreliable travel conditions within cities. This is because business activities depend on the timely delivery of logistics, but productivity in most cases is hindered by the delay in the delivery of freight. Weisbrod and Reno (2009) concurred with the statement by proposing that increased traffic congestion leads to higher costs incurred by commuters and thereby negatively affects business operations.
Cost of transportation
More often than not the impact of vehicular traffic on travelers (the added time) as well as the increased costs of vehicle operators (fuel and spare parts) is the key components of travel system inefficiency (NRC, 1995). Eddington (2006) argues that travel or economic costs of congestion take the form of time wasted through travel delays and unreliable transportation conditions, extra fuel, inability to forecast travel time, environmental damage and related cost to human health. For example, it has been shown that a 15% reduction in average speed in built-up areas may reduce fuel consumption by 20 to 25% (Baker, 1994; NRC, 1992). Furthermore, six times more gasoline is required for a vehicle to start from a complete stop than it does if the vehicle does not come to a complete stop (Baker, 1994).
Infrastructure dilapidation
Pressure on road infrastructure such as bridges and interchanges due to traffic congestion can cause their dilapidation. Bridges on such roads carry the weights of vehicles that have to queue on them. This puts excessive stress on the roads and causes them to wear out. More often than not these roads develop pot holes and failed portions due to the weights of over-loaded articulated vehicles; with time, decay sets in earlier than expected (May and Marsden, 2011; Atash, 2007).
Health
Most of the vehicles on the roads now are powered by derivatives from fossil fuel and other hydrocarbons. The carbon monoxide emitted by them warms up the environment so much that the ozone layer is so badly affected and the infrared wave now penetrates the atmosphere causing the greenhouse effect. The Ozone layer has been seriously depleted resulting in global warming which causes changes in the climate. The emissions from motorized vehicles not only affect the environment but also the health of the individuals. The effect of carbon monoxide on human and animals is devastating. Choking as a result of air pollution, high blood pressure and tension due to road rage are all after-effects of prolonged stays in road traffic congestion (Gardner, 2010).
Al-Mogrin (2005) asserted that lead poisoning occurs more frequently due to traffic. He further identified the symptoms of lead poisoning to include vomiting, constipation or bloody diarrhea with central nervous system effects such as insomnia, irritability, convulsion and even death. For instance, a recent survey on effects of traffic emissions on pregnancy outcomes linked exposure to emissions to adverse effects on gestational duration and possibly also intrauterine growth (Pereira et al., 2010). Other symptoms include headache, weakness, stress and constipation and death due to road accidents (Kayode, 2015; Tamakloe, 1993).
Education
School-related traffic congestion poses threats to the safety of students, teachers, parents, residents, and motorists in and around school locations and this has become a major problem in communities throughout the world. The most obvious cause of traffic congestion around schools is too many vehicles, and the biggest source of those vehicles is parents’ dropping off and picking up their children from school. In the United States, roughly three-quarters of school-aged children are taken to school by car (National Center for Chronic Disease Prevention and Health Promotion, 2001). In the United Kingdom, the share of children taken to school by car is estimated to be between one-third (Derek Halden Consultancy, 2002a, b), and one-half. In both countries, the rate of increase in car transportation of children to school has been significant, often creating serious traffic congestion problems (Kearns and Collins, 2003).
Other factors include changes in school purposes and populations, new school construction, the addition or elimination of busing, and the overall physical infrastructure, street layout, and traffic signs and signals surrounding a school. School traffic congestion is a source of problem for students, school staff, residents in and around schools, and local police charged with enforcing traffic laws and responding to problems raised by residents and schools. More importantly, congestion can be a source of traffic crashes, child pedestrian injuries and death. Child pedestrian injuries due to traffic are more likely to occur in settings with high traffic volume and on-street parking, with children often emerging “masked” from behind parked cars (Porter et al., 2011; Adarkwa, 1991).
Religious activities
Developing countries such as Ghana do experience quite heavy traffic on days when majority go to church. According to Buah (1998), Ghana has close to about 70% of its citizens being Christians. Also, in Takoradi, the STMA (2012) estimated about 83% of the population being Christians and as such on Sundays in particular and during other Christian festive seasons the roads leading to the church zones get congested with vehicles transporting people to the church premises. This kind of congestion is temporal in that after the service, there is no traffic on the roads. However, effects of traffic congestion on church activities include the possibility of people joining different denominations or churches, which in most cases are not pleasing to them or can to lead to members breaking their promises. Such experiences could be challenging as they could even lead to others not attending the church anymore (Buah, 1998).
Recreation
Although initially congestion issues were not addressed within the main tourist road transport externalities, recent trends tend toward a higher use of private or hired cars in tourism destinations (Palmer et al., 2007) and the popularization of the city-break holidays have led to a growing concern about and interest in the contribution of tourism to road traffic congestion. For this reason, city authorities in recent times have become conscious of how the presence of congestion can damage tourist image and how congestion has been recently pointed out as one of the main negative impacts of tourism (Cui and Ryan, 2011). Aguiló et al. (2012), mentioned that, currently cities are developing an interest in applying economic instruments for the regulation of tourism activities in order to yield optimum returns.
This is of special relevance because each country has its own image which is part of its tourist product, but is also susceptible to the effects of transportation problems (Teye, 1992). Traffic congestion, being one major setback of tourism, can reduce the time available for participation in tourist activities and could be perceived as an unsatisfactory experience by visitors. According to Alegre and Cladera (2006), traffic congestion can have a negative effect on a possible future visit by influencing visitors to seek out alternative destinations. For example, there was a $25 million business revenue reduction in Colorado after the percentage of visitors decreased by 1% in 2005 (Development Research Partners, 2007).
Hypothesis
In investigating the relationship between traffic congestion and socio-economic activities, this study has developed this hypothesis: ‘‘There is a significant relationship between severity of traffic congestion and socio-economic activities, namely, work, transportation, education, health, religious activities and recreation in Takoradi’’.
Effects of traffic congestion on work
On average, the expected number of working hours of employees, employed in the formal sector (public and private) in the economy of Ghana is eight hours (Takyi et al., 2013; Lartey, 1977; Adarkwa, 1991). Twenty three percent of the respondents surveyed on Corridor 1 indicated they often reported late to work (Table 1), a situation which Cortright (2009) termed as man productivity loss to time. This finding is also consistent with the discussion by the OECD (2006) and Hon (2005) that traffic congestion affects labour productivity directly since input of labour is directly related to the supply of the labour (OECD, 2006; Hon, 2005). Furthermore, traffic congestion according to an informant on Corridor 5 reduces the economic growth of Takoradi. Hartgen and Fields (2009), in assessing the situation, stated that the effects of traffic congestion on cities’ growth can also lead to a reduction of billions of dollars in productivity and output of the cities. It is therefore important for governments and employers to find ways of improving mobility in such cities since ‘productivity is an investment by a State in transportation while output is the gross domestic product (GDP)’, (Nadiri and Mamuneas, 1996; Okoye et al., 2010; Kayode, 2015). A hawker in an interview however disclosed to the survey team a positive effect of the traffic congestion. This is what she had to say,
‘I make a lot of money during the late morning and evening because a lot of passenger vehicles use the road at these times. I therefore do not miss sales around this time at all’.
Effects of traffic congestion on transport
Respondents who did not own cars explained that it was quite expensive to board vehicles in Takoradi, thus a rise in transport fares was a major challenge to the household. A member of staff at the Department of Urban Roads described the situation in an interview as follows:
‘‘The challenge of traffic congestion is rather appalling especially for private car users who drive over 5 km to work, ‘I have to spend not less than 350.00 Ghana Cedis every month on fuel for my car which is more than 30% of my salary’.
Eddington (2006) and Link (1999) referred to this occurrence as travel cost due to increase in travel delay and need for extra fuel. A household head from Tanokrom also reiterated that; ‘‘It is not advisable for residents to use their own vehicles from areas such as Sekondi to Takoradi to enjoy a particular service. We have no choice since that is the order of the day’’.
Fuel usage and cost of spare parts which according to the NRC (1995) and Eddington (2006) increases cost of driving is a challenge in Takordi as taxi drivers form the bulk of the drivers in the Metropolis. The huge cost incurred by especially public transport drivers on fuel was also found to add an extra burden to their other financial responsibilities like school fees, government taxes and levies. For this reason 10% of the drivers confirmed evading taxes (Table 2), thereby causing the Metropolis loss of funds which could otherwise have been used to provide infrastructure services.
Effects of traffic congestion on education
Majority of the respondents on Corridors 1, 2 and 3 (35, 30 and 23% respectively) complained bitterly about not being able to have the required hours of sleep because of the need to wake up early in order to escape traffic congestion (Table 3). This results in their inability to perform well at work since they not only have to get to work early but also send their wards to school.
According to Porter and Abane (2008) one of the many ways to find solutions to such challenges is to increase children’s participation in transport planning. Most school opening hours are usually from 7:40 a.m. to 8:30 a.m. This is the same time workers also get to work, making some families skip their breakfast or take it while driving. It was shocking to hear from a parent in an interview that he sometimes received calls from teachers, asking her to come and take her son back to the house as punishment for his late-coming. She said:
“It's not like we don't leave early enough. I spend more than half an hour driving from Sekondi before getting to the school and my work place is at the CBD’’.
Effects of traffic congestion on recreation
One major negative impact of traffic congestion in Takoradi is the reduction in revenue obtained by tourism operators especially during the festive seasons. The roads leading to recreational centres such as Takoradi Harbour, Allan Beach and Hotel attract a lot of traffic on the road, which deters tourists from visiting the location. Teye (1992) explained that such situations can lead to unsatisfactory experience by visitors. According to Davison and Knowles (2006), people without private cars or vehicles during festive seasons are disadvantaged in a way as they are compelled to travel by public buses with their attendant delays and discomfort. This can make the tourist feel bad especially when caught in traffic congestion (Cui and Ryan, 2011).
It is however, appropriate to consider that traffic congestion does not always create unfavorable conditions during festive seasons or during periods of tourists’ visit. Some people do benefit from the traffic congestion. For instance most taxi drivers at the taxi ranks in areas around Market Circle explained that they make a lot of sales during festive seasons because most passengers who wish to get to the recreational areas earlier use the taxis to avoid extra waste of time on the road (Table 4). The challenge however is the difficulty on the part of tourists to pay the huge amount charged by the drivers. Fifty-five percent of the traders also at Market Circle stated that they make higher sales during such occasional seasons. A shopkeeper in an interview said:
‘Most customers prefer to buy around festive seasons like Christmas and they do that very early in the morning, that is during the rush hours since they believe that is the time they will get fresh goods especially the perishable ones to buy’.
Effects of traffic congestion on health and environment
Pollution from vehicles is usually inhaled by passengers caught in a traffic congestion and people working in firms and companies located around arterial roads (Al-Mogin, 2005). In Takoradi, however, people who inhale the unfavourable gases comprise mostly sellers along the roads around the Market Circlet. A commuter in an interview explained the situation as follows:
‘‘I can’t stay long in traffic since inhaling fumes from the cars chokes me’’
This statement agrees with the assertion from the World Watch Institute (2008) that prolonged stay in road traffic leads to choking due to pollution. Kayode (2015) agreed with Al-Mogrin (2005) that lead poisoning which is often caused by inhaling polluted air in a traffic congestion can cause headache, weakness of the body, stress, constipation and death.
Most of the ‘trotros’, according to an officer at the MTTU, are not in good condition and therefore produce harmful gases such as Carbon Monoxide which are risky to inhale. An official of the GPRTU also expressed the challenge as follows:
‘‘I wish most of the ‘trotros’ that have out-lived their expected number of years are stopped from using the road but nothing like that has ever been done to regulate the types of vehicles on the roads since I began working in the Metropolis’’.
Effects of traffic congestion on religious activities
Most respondents reported being late for religious activities due to traffic on the five corridors studied (Table 5). A majority of this group which comprised of Muslims complained of heavy traffic during their festive seasons (IdirFitir and IdirAdhar) because of the location of the central mosque. One of the mosques is located close to the Tarkwa station, and the other is also located close to the Segou area. This situation increases vehicular traffic on the road as there are a lot of people plying these roads, while the festivity also attracts a lot of people from adjacent towns. According to informants, the Jumah or Friday prayers also make such roads highly congested. An appeal, therefore, was made for the relocation of the mosque by one Imam (Prayer Leader) in the Metropolis. A resident at Effiakuma explained this as follows, ‘‘We hear the sound of trotros and their ‘mates’ shouting for passengers to board their vehicles making it difficult sometimes for us to concentrate at church’’.
Test of hypothesis
Table 6 shows the test of hypothesis which guided the study. The hypothesis is stated as follows: The data as shown in Table 7 were generated by asking all respondents interviewed, 24 each of the 5 corridors (Table 8) studied to indicate their views on the severity of congestion on the roads. This was done by using a Likert Scale as discussed earlier. Using the same Likert Scale, the severity of traffic congestion was used to predict the major socio-economic effects acknowledged by the respondents as significant predictor of traffic congestion on the individual roads appraised. The test performed with a significant value of 0.05 allowed for the determination of the level of relationship between severity of traffic congestion on the 5 arterial roads and socio-economic activities. From Table 8, socio-economic effects of traffic congestion represent dependent variables while the independent variable is represented by traffic congestion severity on the various roads.
Corridor 1, that is, areas in and around Takoradi Market Circle, recorded no significant relationship between delay to places, stress and fuel consumption. However, there is a significant relationship between traffic severity and probability of accident occurring (p value = 0.012) and reduction in worker productivity (p value = 0.042) and severity of traffic congestion. Again, on Corridor 1 there is also a significant relationship between traffic congestion and increase in prices of goods and services (p value: 0.015) and severity of traffic congestion. This could be as a result of the time taken for workers especially those employed in the formal sectors to drive through the heavy traffic at Market Circle before they get to their work places. This reduces their working hours and reduces economic growth of the city of Takoradi (Takyi et al., 2013; Harten and Fields, 2009).
On Corridor 2, however, the significant relationship between traffic congestion and road accidents can be as a result of transporting cargo from the port to Sekondi using the intersection at Paa Grant Circle. The trucks produced a lot of fumes and moved slowly. This can also be as a result of the several roads joining the circle which makes it imperative for drivers to be extra vigilant when joining the road. For this reason, officials from the MTTU are mostly assigned to the circle to control the flow of the traffic in order to prevent possible accidents.
On Corridor 4, the negative relationship between traffic congestion and prices of goods and services could be due to the fact that most shop owners along the road to Tanokrom patronize their goods from the Market Circle and resell them to the residents in the suburbs. The sellers do not increase the prices so much because it does not cost much to commute to the Market from their shops.
On Corridor 5, however, a positive relationship between traffic congestion and delays implies that passengers and drivers that used the road or the Circle in the morning rush hours get to their destinations late. This relationship is consistent with the data from the Department of Urban Roads that Zone 5 is the most congested place among the 5 corridors and also the assertion by the OECD (2006) that productivity of labour is directly related to the supply of the labour.
