This is a guest post by Ann Larson. Ann Larson is a demographer specializing in evaluating regional development and global health programs. She blogs from her home in rural Western Australia.

In a recent tweet Demotrends shared a media report that France’s fertility was dipping below 2 children per woman.  Doom was predicted to inevitably follow—French women’s relatively high fertility was seen as the nations’ greatest economic advantage against her prosperous but low-fertility rival, Germany.  Many similar articles have been and will be written.

What twaddle.

Whether you look backwards or forwards, French fertility and French couples are doing exactly what they have done for a long time and–every sign is–will continue to do into the future.

France holds a special place in the heart of demographic historians because it is in the French data that Louis Henry and Jean Bourgeois-Pichat found evidence of the earliest widespread and sustained decline in fertility. Van de Walle later confirmed that France had two fertility transitions; the first very early one and the second in the late 19^th century in line with other European countries and English speaking settler societies. (See John C Caldwell’s great potted history of fertility declines in the time of social upheaval for more on studies of French fertility here.)    So French families have a very long history of controlling their fertility, and the national fertility level has been around or below replacement during WWI, in the 1920s and since the 1970s (INSEE for 1946 to present, and a longer trend in Wikipedia).

Now looking forward, changes in period measures of fertility data appear more meaningful than they really are when fertility is low. For the past 10-15 years demographers have been trying to tease out the ‘tempo’ changes to period fertility measures from the more significant changes in lifelong, or cohort fertility.  Tempo reflects fleeting changes in the timings of births due to delayed or accelerated childbearing in response to shifts in preferred age at childbearing and in response to temporary economic conditions or government policies.  It is changes in cohort fertility that really matter and that, for cohorts under age 40 or 45, is difficult to measure.

In March 2013 Population and Development Review published a refreshing article by Myrskylä, Goldstein and Cheng. They used a deceptively simple method to project cohort fertility for women born in the 1970s, based on past five-year trends in period fertility.  The method is very good at describing past fertility which gives us confidence that their short term projections will be valid as well. What they show is that in all countries where period fertility is around replacement (a little over 2 to 1.7 or 1.8) cohort fertility is likely to be in the high range of that measure.  For most (but not all) very low fertility countries, cohort fertility is also likely to be higher, in the range of 1.7 or 1.8.

Low fertility is a contemporary reality; we need to celebrate that world population is no longer growing rapidly and that at the same time life expectancy is increasing. Unless low fertility is coupled with other demographic phenomenon, such as widespread out migration of young adults, countries that have a century or more of experience of low fertility will not have a sudden demographic collapse.

Blips in period fertility rates of low fertility countries are not the sky falling in, but are no more significant than Chicken Little’s acorn falling from a tree.