The Combine Oral Contraceptive Pill (COCP), often referred to as "the Pill", is a combination of an estrogen (oestrogen) and a progestin (progestogen), taken by mouth to inhibit normal female fertility. Combined oral contraceptives were developed by Gregory Goodwin Pincus, John Rock, and Min Chueh Chang. They were first approved for contraceptive use in the United States in 1960, and are still a popular form of birth control. They are currently used by more than 100 million women worldwide and by almost 12 million women in the United States. Usage varies widely by country, age, education, and marital status: one quarter of women aged 16–49 in Great Britain currently use the Pill (combined pill or minipill), compared to only 1% of women in Japan.