## Doubling time and population increases among the Old Order Amish

William McGuigan, *Pennsylvania State University*

Old Order Amish are a secluded religious group that began in Switzerland in 1693 from Swiss and Alsatian Anabaptists who immigrated to the United States from the Palatine region of Germany, leaving no Amish in Europe. A 2008 study suggested the Amish population had increased to 227,000 and in 2010 a study suggested their population had grown by 10 percent in the past two years to 249,000, with increasing movement to the western states. While most Americans have had a birthrate too low to maintain the population since the early 1970s, the Amish continue to have 6–7 children while benefiting from the decrease in infant and maternal mortality in the 20th century. Some studies claim that between 1992 and 2013, the Amish population increased by 120% while the US population increased by only 23%. These estimates of Amish population growth cite a "doubling time" but do not substantiate the source from which the estimate was derived. A precise counting of children and adults would be near impossible but the current study provides a calculation of "doubling time" based on the net change in the number of Amish households from hundreds of Amish settlements over the last five years. Information of the number of households in an Amish settlement provides the mean to calculate a more scientifically established and statistically precise doubling time number. Assuming a constant rate of change, doubling time is the logarithmic value for the number 2 (doubling), divided by the logarithmic value for the value derived from the number of households at time 2 divided by the number of households at time 1. Or, using the "rule of 70", the natural log value of 2 divided by the rate of change. This finds the doubling time for the Amish population in the US to be 21.03 years.

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Presented in Session P1. Poster Session 1