Russia’s invasion of Ukraine has created one of the biggest refugee crises of modern times, according to a Pew Research Center analysis of United Nations data. A month into the war, more than 3.7 million Ukrainians have fled to neighboring countries, the sixth-largest refugee outflow over the past 60-plus years by total number of refugees. They represent about 9.1% of Ukraine’s pre-invasion population of about 41.1 million, ranking the current crisis 16th among 28 major refugee crises by share of population.