GDP per worker is the ratio of GDP (Y) to the number of people employed (N), it is Y divided by N. Some books denote it as little Y (y). Divide both sides of the production function by N (remember to use the rules of dividing exponents for N on the left hand side i.e. subtract the exponents, for N it will be 2/3-1 = 1/3). 

Simplify the equation, so on the left hand side you should have (K/N) raised to the power of 1/3. You can replace this fraction with little k (k), raised to the power of 1/3. The little k represents capital per worker then.



1) $$ Y = A K^{1/3} N^{2/3} $$

2) Divide by N

3) $$ Y/N = A K^{1/3} N^{2/3-1} $$

4) $$ Y/N = A K^{1/3} N^{-1/3} $$

5) $$ Y/N = A (K/N)^{1/3} $$

6) $$ y = A (k)^{1/3} $$