The USSR practiced some form of central planning beginning in 1918 with War Communism until it dissolved in 1991, although the type and extent of planning was of a different nature before imperative centralized planning was introduced in the 1930s. While there were many subtleties to the various forms of economic organization the USSR employed during this 70-year time period, enough features were shared that scholars have broadly examined advantages and disadvantages of Soviet-type economic planning. Soviet is not the same as economic planning in general – there are other theoretical models of economic planning, and modern mixed economies also practice economic planning to a certain extent, but they are not subject to all of the advantages and disadvantages enumerated here.