Google is failing me, especially in terms of how specifically people perished. Was it from collectivization, famine, execution? The estimates available seem uncertain, even from reputable sources. Thanks for any help.
This site cites several death count estimates. The reputable ones seem to cluster around 20 million. One of the estimates cited breaks it down roughly into 12 million in the various Gulag camps, 7 million in famine, and 1 million in executions.