Serving in the Politburo was a part-time function, and members served concurrently in either the party, state, trade union, security or military administrations (or all of them concurrently). Until the 1950s, most members served in state positions, but this changed at the 20th Congress (held in 1956) when 47% percent of Politburo members served in the central party apparatus while another 47% served in the state administration. From the 20th Congress until the 28th Congress, the share of Politburo members serving in the central party apparatus increased, while those serving in the state administration declined. The majority of Politburo members had leading central posts; the highest share of republican officials serving in the Politburo came at the 22nd Congress (held in 1961) when 50 percent of members held offices at the republican-level.