Short-run production function
Ranges of the production function

The following table and simple production function is based on an imaginary maize farmer.  (more)

Total product rises at an increasing rate until the 4th unit of labour is employed.  

After the 4th unit, total product still rises but at a diminishing rate until the employment of the 8th unit of labour.

The employment of the 9th unit of labour does not contribute anything to total product;  no change  in the total product takes place. 

The employment of the 10th unit of labour causes a decline in total product from 200 to 187. 

An important relationship exists between the total product, the average product and the marginal product. 

Units of land Units of labour
(N)
Total 
product
(tons)
Increase at a increasing/
diminishing rate
20 0 0  
20 1 16  Increasing
20 2 44 Increasing
20 3 78 Increasing
20 4 113 Increasing
20 5 145 Diminishing
20 6 171 Diminishing
20 7 190 Diminishing
20 8 200 Diminishing
20 9 200 None
20 10 187 Decrease

The law of diminishing returns states that as more of a variable input is combined with one or more fixed inputs in a production process, the marginal product of the variable input will eventually decline.   The decline in the marginal product of the variable input is followed by a decrease in the average product and lastly by a decrease in the total product. (more)