Between 1945 and 1989, the share of ethnic Estonians in the population resident within the currently defined boundaries of Estonia dropped to 61%, caused primarily by the Soviet programme promoting <answer>mass immigration of urban industrial workers from Russia, Ukraine, and Belarus</answer>, as well as by wartime emigration and Joseph Stalin's mass deportations and executions.[citation needed] By 1989, minorities constituted more than one-third of the population, as the number of non-Estonians had grown almost fivefold.
What trend caused the drop of ethnic Estonians?
mass immigration of urban industrial workers from Russia, Ukraine, and Belarus