In 1949 a new constitution was promulgated, creating a Senate appointed by the king (in practice, by the government). But in 1951 the regime abolished its own constitution and reverted to the 1932 arrangements, effectively abolishing the National Assembly as an elected body. This provoked strong opposition from the universities and the press, and led to a further round of trials and repression. The regime was greatly helped, however, by a postwar boom which gathered pace through the 1950s, fuelled by rice exports and U.S. aid. Thailand's economy began to diversity, while the population and urbanisation increased.