This interministerial working group prepared population prospects with different fertility assumptions, fertility being rightly considered the main determinant of ageing. It did not foresee
an increase of life expectancy, the second determinant of ageing.
And it was cautious as to immigration of foreigners in the years after the recruitment stop in 1973; the three migration assumptions were: zero, 20 000 annual net immigration and 55 000 annual net immigration