What is the expected number of abortions among nurses over this time period if the incidence of abortion is 25 per 1000 women per year and no woman has more than 1 abortion?

Studies have been undertaken to assess the relationship between abortion and the development of breast cancer. In one study among nurses (the Nurses’ Health Study II), there were 16,359 abortions among 2,169,321 person-years of follow-up for women of reproductive age. (1 person year = 1 woman followed for 1 year.)