Taiwan's population structure has undergone great changes over the last few decades. The economically productive 15-64 age group increased from 56.40 percent in 1949 to 70.93 percent in 2003. The declining birth rate led to a decrease in the 0-14 age group from 41.11 percent to 19.83 percent over the same period. Medical advances have brought about an increase in the proportion of elderly from 2.50 percent to 9.24 percent. Although this raised the proportion of elderly dependents to 13 percent, the total proportion of dependents dropped to 41 percent in 2003 due to the falling birth rate. At 100:104, the ratio of females to males held steady in 2003.