At first there is neither much contraceptive use nor much unmet need because most couples do not want to, or are unaware that they can, limit or space births. Fertility is high. As more couples want to control their fertility, unmet need rises because attitudes change faster than contraceptive use rises. Contraceptive use begins to rise as well, however, and the fertility rate starts to decline. Reproductive attitudes continue to change and, as information and services respond to people's changing attitudes, contraceptive use rises rapidly, while unmet need declines.
Fertility often declines rapidly.
Finally, most women do not want more children, and use of family planning is widespread. There is little unmet need remaining. Fertility stabilizes at a lower level than before. In countries with high contraceptive prevalence, the level of unmet need is low. At lower levels of contraceptive use, the level of unmet need is high, with slightly lower levels of unmet need in countries with the very lowest levels of contraceptive use.