As economy grows, there is a shift in labour force from Primary Sector to Secondary and Tertiary Sectors. As economy progresses, the people tend to work more in the secondary and service sectors of the economy. Workforce of primary sector gradually starts decreasing with the economic development. Hence, there is an increase in demand for goods and services produced by secondary and tertiary sectors. As a result, the share of secondary and tertiary sectors to the GDP increases and the share of primary sector to the GDP decreases.