Crimea may have a majority Russian population today, but it hasn't always been that way.

The peninsula's dark history of ethnic cleansing is visible in the following chart from Reuters.

The chart shows a collapse in the population of native Crimean Tatars from 34.1% in 1897 to zero in 1959, marking brutal harassment leading up to Soviet leader Joseph Stalin's forcible deportation of the entire population in 1944, with nearly half dying in the process. It took decades for the population to climb back to 12% by 2001.

While the population of Ukrainians and especially Russians rose, the percentage of the population falling into an unlisted category also fell from more than 20% in 1921 to around 5% in 1959. This was a consequence of the deportation of Armenians, Bulgarians, Greeks, and other groups.

With a history like this — and a similarly tragic history across Ukraine — it's not hard to see why many say it is unfair not to mention illegal to make Crimeans take a referendum on joining Russia.