Background Information about the incidence of induced abortion is needed to motivate and inform efforts to help women avoid unintended pregnancies and to monitor progress toward that end. We estimate subregional, regional, and global levels and trends in abortion incidence for 1990 to 2014, and abortion rates in subgroups of women. We use the results to estimate the proportion of pregnancies that end in abortion and examine whether abortion rates vary in countries grouped by the legal status of abortion. Methods We requested abortion data from government agencies and compiled data from international sources and nationally representative studies. With data for 1069 country-years, we estimated incidence using a Bayesian hierarchical time series model whereby the overall abortion rate is a function of the modelled rates in subgroups of women of reproductive age defined by their marital status and contraceptive need and use, and the sizes of these subgroups. Findings We estimated that 35 abortions (90% uncertainty interval [UI] 33 to 44) occurred annually per 1000 women aged 15–44 years worldwide in 2010–14, which was 5 points less than 40 (39–48) in 1990–94 (90% UI for decline −11 to 0). Because of population growth, the annual number of abortions worldwide increased by 5·9 million (90% UI −1·3 to 15·4), from 50·4 million in 1990–94 (48·6 to 59·9) to 56·3 million (52·4 to 70·0) in 2010–14. In the developed world, the abortion rate declined 19 points (−26 to −14), from 46 (41 to 59) to 27 (24 to 37). In the developing world, we found a non-significant 2 point decline (90% UI −9 to 4) in the rate from 39 (37 to 47) to 37 (34 to 46). Some 25% (90% UI 23 to 29) of pregnancies ended in abortion in 2010–14. Globally, 73% (90% UI 59 to 82) of abortions were obtained by married women in 2010–14 compared with 27% (18 to 41) obtained by unmarried women. We did not observe an association between the abortion rates for 2010–14 and the grounds under which abortion is legally allowed. Interpretation Abortion rates have declined significantly since 1990 in the developed world but not in the developing world. Ensuring access to sexual and reproductive health care could help millions of women avoid unintended pregnancies and ensure access to safe abortion.