A stork and baby correlation:
People have had a little fun pointing out that there is a correlation between storks and babies. Nobody takes it seriously, but I was curious as to where the story came from. The rumor is that the more storks that fly into Germany, the more babies are born. So I looked for a reference. One was by Robert Matthews Aston University, Birmingham, England. e-mail: email@example.com in Teaching Statistics. Volume 22, Number 2, Summer 2000. The link is http://www.uni-marburg.de/fb21/motologie/mitarbeiter_seiten/ls/storks.pdf
He presents this graph of the number of storks in various European countries and the number of babies born in each country.
The correlation was such that there was one chance in 125 that the correlation was pure chance and there was no actual causal relationship. They attribute the correlation to the concept that bigger countries have more storks and more babies. Nice, but the thought was that this was going on in Germany.
I found another site:
http://www.astro.umd.edu/~peel/CPSP118D/Stork_article.pdf with an article New evidence for the Theory of the Stork, Thomas Höfera, Hildegard Przyrembelb and Silvia Verlegerc, aFederal Institute for Risk Assessment, Berlin, bOffice of the National Breast Feeding Committee at BfR, Berlin, and cIndependent Midwife, Berlin,Germany © Blackwell Publishing Ltd. Paediatric and Perinatal Epidemiology 2004, 18, 88–92 that did confine its interest to Germany. They found a correlation between the number of babies born at home and the number of storks. You had to exclude babies born in hospitals, and as they point out there are no storks in hospitals. I have been unable to copy their graph, but both storks and babies declined between 1970 and 2000 with a dip and recovery between 1975 and 1990. Actually the babies then returned to trend, but the storks did not return to trend, increasing a bit. Maybe that is the source of the story, but the article includes earlier references, notably Sies H. A new parameter for sex education. Nature 1988; 332:495. I have not run it down, but if one were interested in finding the source, that would be a good place to start.
Meanwhile I found a charming reference to a blue stork seen in Germany last year. http://www.treehugger.com/natural-sciences/blue-stork-finds-true-love-in-spite-of-curious-color.html There are pictures.
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