Russia has moved to classify key demographic statistics following a dramatic collapse in its birth rate, which has plunged to levels not seen since the late 18th or early 19th century, according to a leading Russian demographer.

For decades, Russia has been experiencing a plunging birth rate and population decline, which appears to have worsened amid its ongoing invasion of Ukraine—with high casualty rates and men fleeing the country to avoid being conscripted to fight.

Projections estimate that Russia’s population will fall to about 132 million in the next two decades. The United Nations has predicted that in a worst-case scenario, by the start of the next century, Russia’s population could almost halve to 83 million.