The Ninth-of-May Constitution declared the government's intention to collectivise agriculture. In February 1949, the National Assembly adopted the Unified Agricultural Cooperatives Act. Cooperatives were to be founded on a voluntary basis; formal title to land was left vested in the original owners. The imposition of high compulsory quotas, however, forced peasants to collectivise in order to increase efficiency and facilitate mechanisation. Discriminatory policies were employed to bring about the ruin of recalcitrant kulaks (wealthy peasants). Collectivisation was near completion by 1960. 16% of all farmland (obtained from collaborators and kulaks) had been turned into state-run farms. Despite the elimination of poor land from cultivation and a tremendous increase in the use of fertilisers and tractors, agricultural production declined seriously. By 1959, pre-war production levels still had not been met. Major causes of the decline were the diversion of labour from agriculture to industry (in 1948 an estimated 2.2 million workers were employed in agriculture; by 1960, only 1.5 million); the suppression of the kulak, the most experienced and productive farmer; and the peasantry's opposition to collectivisation, which resulted in sabotage.