It gets even WORSE.
Someone (who is more mathematically inclined than I) should calculate the effect of shorter generational reproduction times.
E.g., a muslim generation of making babies every 17 years versus the average French couple that might wait to make its babies every 30th year.
In other words, they're making MORE babies, and they're making them MORE OFTEN, quicker, SOONER.
Just my $0.02.
A proper demographic analysis would do just that.
Remember, it's illegal in France for their census officials to ask the questions needed in order to get the data needed to do the analysis.
In other words, THE FRENCH DON'T WANT TO KNOW.
The French have a fatal case of PC.