Between 1874 and 1921, the total population increased from about 946,000 to 2.4 million. By 1950 it had increased to between 3,710, 107 and 4,073,967, and in 1962 it had reached 5.7 million. From the 1960s until 1975, the population of Cambodia increased by about 2.2 percent yearly, the lowest increase in Southeast Asia. By 1975 when the Khmer Rouge took power, it was estimated at 7.3 million. Of this total an estimated one million to two million reportedly died between 1975 and 1978. In 1981 the PRK gave the official population figure as nearly 6.7 million, although approximately 6.3 million to 6.4 million is probably a more accurate one. The average annual rate of population growth from 1978 to 1985 was 2.3 percent (see table 2, Appendix A). Life expectancy at birth was 44.2 years for males and 43.3 years for females in 1959. By 1970 life expectancy had increased by about 2.5 years since 1945. The greater longevity for females apparently reflected improved health practices during maternity and childbirth.

In 1959 about 45 percent of the population was under 15 years of age by 1962 this figure had increased slightly to 46 percent. In 1962 an estimated 52 percent of the population was between 15 and 64 years of age, while 2 percent was older than 65. The percentage of males and females in the three groups was almost the same.

The population of Cambodia has been fairly homogeneous. In 1962 about 80 percent of the population was ethnic Khmer. The remaining 20 percent included Chinese, Vietnamese, Cham, Khmer Loeu (see Appendix B), Europeans. By 1981, as a result of the Vietnamese repatriation in 1970 to 1971 and the deaths and emigration of large numbers of Cham and Chinese, ethnic Khmer accounted for about 90 percent or more of the population.

Data as of December 1987