Simon, to reply to your comment. In my construct it doesn't matter at what age someone enters the job market because if you assume that:

-people born within a relatively medium/long period of time - let's say 20 years (as in 1975 - 1995) - all enter the market with similar distribution across age groups

-that the population and employment rate are relatively stable over a similar medium/long period of time (as in 1993-2013)

then what that means is that in each year during that period you will have a total population that enters the job market that is equal to the sum of the populations across different age groups that enter the job market that year. However since we just assume that people born in different year enter the job market with similar distribution across age groups and that population and employment are constant, what that means is that that number is equal to just the total % of people of a given year of birth who will ever enter the job market.

To help make this more practical using numbers, let's assume the following:

- people born per year: 100 (constant)

-people enter job market in only 4 years after birth, the distribution across which and sum of is constant across different birth years (this example assumes 80% of people born will go to work): year 1: 5 people, year 2: 15 people, year 3: 35 people, year 4: 25 people

In year 5 and following (equilibrium) the people that enter the market each year are:

people born in year 5-1 (year 1 of their life) ---> 5

people born in year 5-2 (year 2 of their life) --> 15

people born in year 5-3 (year 3 of their life) --> 35

people born in year 5-4 (year 4 of their life) --> 25

total # of people entering the job market in year 5 --> 80 which is the same number of people who will eventually find employment during their life span for years 1,2,3,4

Hope this clarifies a bit,

Andrea