Economic growth elements
Development of a city mainly depends upon its financial strength, hence economic development is fundamental to city change and urban expansion. Urban land use is actually a comprehensive economic issue, while gross domestic product (GDP) is an integrated index reflecting the national economic development status of a region. Since reform and opening to the outside, rapid economic development has been achieved in Guangzhou. Guangzhou's GDP was US$ 0.642 billion in 1980, US$ 2.902 billion in 1988, US$ 15.018 billion in 1995, US$ 36.263 billion in 2002, which means an increase of 55.5 times of the GDP in 1980. As shown by the analytical results of the relationship between the two parameters, the built-up urban area is highly correlated with the GDP of Guangzhou City. Through curve fitting, an optimized binomial fitting equation y = 0.0063x2 − 1.0184x + 20.547 can be derived, with the total correlation coefficient being 0.9851 (Fig. 5), demonstrating that the economic development of a city is a key driving force for urban land expansion.