The nation-state was new. So too were its citizens, as a result of two sweeping social changes. Beginning in the early 19th century, the landscape and society of the lower Chao Phraya basin were transformed by a frontier movement of peasant colonization. Uniquely in Asia, new land was being opened up faster than the population was growing from the mid-19th century right through to the 1970s. As a result of political decisions in the late 19th century, this frontier society was characterized not by landlords but by peasant smallholders. Until urbanization accelerated in the last quarter of the 20th century, this peasant smallholder society represented four-fifths of the population and was the main driving force of the economy.