A population of 100 healthy women was recruited from the internal medicine practice at University Medical Center (UMC) from June 1 - June 30, 2000 and followed for the development of breast cancer. Twelve women developed breast cancer after each was followed for 4 years. Ten women who remained healthy were followed for 2 years and then were lost to follow-up. Five women died of heart disease after 6 years of follow-up. These five women did not develop breast cancer. The remaining women remained healthy and were each followed for 10 years.

Are the 100 women who enrolled in the study members of a fixed or dynamic population?