> As a non-provocative question, did collectivization *ever* improve
> agricultural productivity?
If you mean Soviet-style collectivization, the record is ambiguous -- the Soviet system did raise productivity, through massive infrastructure projects, fertilizer plants, industrial processing, literacy campaigns, etc. It also destroyed productivity, through massive waste, monopolistic requisition systems, and ecological stripmining.
If we're talking other countries, we have to be specific about the context and time-period: China pursued highly successful agrarian policies from 1949-1956, disastrous policies from 1957-1979, and returned to sanity in 1979.
-- DRR