In European countries which were most profoundly influenced by the Reformation, Protestantism still remains the most practiced religion. These include the Nordic countries and the United Kingdom. In other historical Protestant strongholds such as Germany, the Netherlands, Switzerland, Latvia, Estonia and Hungary, it remains one of the most popular religions. Although Czech Republic was the site of one of the most significant pre-reformation movements, there are only few Protestant adherents; mainly due to historical reasons like persecution of Protestants by the Catholic Habsburgs, restrictions during the Communist rule, and also the ongoing secularization. Over the last several decades, religious practice has been declining as secularization has increased. According to a 2012 study about Religiosity in the European Union in 2012 by Eurobarometer, Protestants made up 12% of the EU population. According to Pew Research Center, Protestants constituted nearly one fifth (or 17.8%) of the continent's Christian population in 2010. Clarke and Beyer estimate that Protestants constituted 15% of all Europeans in 2009, while Noll claims that less than 12% of them lived in Europe in 2010.
The Pew Research Center estimated Protestants to be what percentage of Europe's Christian population in 2010?
17.8%