During the second period, called the "construction of the foundations of socialism," agriculture was collectivized, and industry was diversified into mining, timber processing, and consumer goods production. Central planning of the economy began in 1931 with an abortive five-year plan and with annual plans in 1941; five-year plans began anew with the First Five-Year Plan (1948–52). Soviet, and after 1949 Chinese, aid increased, allowing the construction of the Trans-Mongolian Railway – the Ulaanbaatar Railway – and various industrial projects. Although industrial development still was concentrated in Ulaanbaatar, economic decentralization began with the completion of the Ulaanbaatar Railroad and the establishment of food processing plants in aimag centers.