Eg: The number of aged people over 65 increased significantly from 1940-2000.

　　The number of aged people over 65 dropped slightly from 1960-1980.

　　The number of aged people over 65 fluctuated between 1 million and 1.2 million from 1940-1950.

　　The number of aged people over 65 remained stable from 1930-1940.

　　句式二: There be + 形容词 + 表示趋势的名词 + in+ 变化的主体+ 时间区间

　　Eg: There was a significant increase in the number of aged people over 65 from 1940-2000.

　　There was a slight decline in the number of aged people over 65 from 1960-1980.

　　There was a fluctuation between 1 million and 1.2 million from 1940-1950.