WASHINGTON, April 30 (UPI) -- The news that France has overtaken Ireland to boast the highest birthrate in Europe is intriguing for three different reasons.

The first is that for a Europe that is worried about too few children being born to support the fast-growing numbers of elderly retirees, it suggests that public policy can make a difference. France now pays any mother with a third child about $1,200 in child support, along with massive discounts on train and public transport and subsidized day care. These incentives seem to work.

The second development to note is that INED, France's National Institute of Demographic Studies, has done some detailed research and concluded that France's immigrant population is responsible for only 5 percent of the rise in the birthrate and that France's population would be rising anyway even without the immigrant population.

That is important in a country where the number of immigrants from traditionally Muslim countries and their French-born children and grandchildren is now reckoned to be more than 6 million from a total population of 60.7 million. The anti-immigration Front National Party has claimed the rise in births came from Muslims, who were thus on track to become an eventual majority, and this appears not to be the case.

In fact in France, like everywhere else in Europe, the birthrate among immigrant mothers drops quickly toward the local norm in less than two generations. The measure most commonly used in international statistics is the Total Fertility Rate, which seeks to measure the number of children born to the average woman in her fertile years. (The formal definition of TFR is the average number of children a woman would have during her reproductive lifetime if current age-specific fertility rates remained constant over her reproductive life.)