At least 3.9 million unauthorized migrants – and possibly as many as 4.8 million – lived in Europe in 2017 with half of them in Germany and the United Kingdom, according to a study published Wednesday. The Pew Research Center said the number grew from 2014, when about 3-3.7 million resided in Europe, and peaked in 2015-16 during the refugee crisis when some 1.3 million people arrived, mostly from war-torn countries such as Syria, Iraq and Afghanistan. In 2016, an estimated 4.1-5.3 million unauthorized migrants lived in Europe. That´s the year central European countries closed the Balkans route that many migrants used to get to northern Europe. Also, the European Union and Turkey signed a deal designed to keep millions of migrants in Turkey from coming to Europe, and many asylum seekers, especially Syrians, received asylum or residency rights in Germany and other European countries. All this led to a decrease in the number of unauthorized migrants by 2017. The findings are based on the latest available data from all 28 EU member states as well as Norway, Switzerland, Iceland and Liechtenstein. Even with the growth of migration to Europe, unauthorized migrants accounted for less than 1% of the continent´s total population of more than 500 million in 2017. That´s less than half the percentage for the United States, which in 2017 had an estimated 10.3-10.7 million unauthorized immigrants – or 3% of a population of 325 million. The Washington D.C.-based Pew Research Center defines unauthorized migrants as people living in a country without citizenship and without residency permits. The center also includes asylum seekers with a pending decision on their asylum request as unauthorized because asylum rejection rates are high. Also, children born to unauthorized migrants in Europe are considered unauthorized themselves because most European countries do not have birthright citizenship. In the US everybody born in the country is an American citizen, regardless of their parents´ immigration status.