Ukraine’s population has been shrinking fast — a trend that started long before Russia annexed Crimea in March, and 4 percent of Ukraine’s population with it. Ukraine’s population declined by 6.3 million people, or 12 percent, between 1990 — the year before it gained independence from the Soviet Union — and 2012, the latest year for which the government has released estimates. And the United Nations projects the trend will continue: In the most likely scenario, Ukraine’s population will dip below 34 million in 2050, or less than two-thirds its population at independence.