Agriculture in the Soviet Union was mostly collectivized, with some limited cultivation of private plots. It is often viewed as one of the more inefficient sectors of the economy of the Soviet Union. A number of food taxes (prodrazverstka, prodnalog, and others) were introduced in the early Soviet period despite the Decree on Land that immediately followed the October Revolution. The forced collectivization and class war against (vaguely defined) "kulaks" under Stalinism greatly disrupted farm output in the 1920s and 1930s, contributing to the Soviet famine of 1932–33 (most especially the holodomor in Ukraine). A system of state and collective farms, known as sovkhozes and kolkhozes, respectively, placed the rural population in a system intended to be unprecedentedly productive and fair but which turned out to be chronically inefficient and lacking in fairness. Under the administrations of Nikita Khrushchev, Leonid Brezhnev, and Mikhail Gorbachev, many reforms (such as Khrushchev's Virgin Lands Campaign) were enacted as attempts to defray the inefficiencies of the Stalinist agricultural system. However, Marxist–Leninist ideology did not allow for any substantial amount of market mechanism to coexist alongside central planning, so the private plot fraction of Soviet agriculture, which was its most productive, remained confined to a limited role. Throughout its later decades the Soviet Union never stopped using substantial portions of the precious metals mined each year in Siberia to pay for grain imports, which has been taken by various authors as an economic indicator showing that the country's agriculture was never as successful as it ought to have been. The real numbers, however, were treated as state secrets at the time, so accurate analysis of the sector's performance was limited outside the USSR and nearly impossible to assemble within its borders. However, Soviet citizens as consumers were familiar with the fact that foods, especially meats, were often noticeably scarce, to the point that not lack of money so much as lack of things to buy with it was the limiting factor in their standard of living.