PIP: Differences in urban and rural populations in China stem from rural to urban migration and differences in the distribution of births in urban and rural areas. Differential fertility has been evident over the past 40 years. There has been a consistently higher rural fertility rate, even though urban population has been expanding. Fertility rates were charted for the period 1954 to 1990 annually for each area: cities, counties, and the differences. Findings indicated that the proportion of urban population did not increase as fast as the number of cities and towns. The proportion of urban population increased 15.63% from 1949 to 1990; the ratio of proportion to size was 1.0:2.8. An imbalance in the urban and rural fertility rates influences urbanization. If urban and rural rates had been the same, rural population size would have been estimated at 908.23 million or, accounting for migration, 734.02 million in 1990. Actual urban population was 837.17 million or a difference of 103.15 million. An estimation of the proportion of urban population with similar rates of fertility with rural areas would have produced 28.77%, but census figures indicate urbanization to be 26.23%. The imbalance in urban and rural fertility rates has increased urbanization by 2.54%. If estimation of rural population is only considered from 1962, rural population would have been 234.707 million less than the actual amount, and the proportion urban at the end of 1961 was 32.98% or 6.75% higher than the proportion in 1990. The direct influence on urbanization statistically could have been 2.54% or 6.75%. A lower population in rural areas would have meant greater economic advantages in urban areas that would have promoted urbanization, and the level of economic development would have increased. Thus, the same urban and rural fertility rate would eventually have had little influence on urbanization. Rates could be the same if underlying conditions were equalized: age structure, marriage rates, economic development, educational level, employment rate, and population policy. Changes in these factors in rural areas is long term and it is unlikely the rural and urban fertility will be the same.