New Zealand's fertility rate began decreasing in the 1870s. The main reasons were an increase in the age of women marrying, fewer women marrying, and social changes such as more women working in cities. The declining birth rate concerned the government, which allowed the Post and Telegraph Department to destroy packages containing references to contraceptives in 1906, and banned publication of contraceptive advice in 1910. The fertility rate climbed in the 1940s and peaked in the early 1960s. Following the introduction of the pill in 1961 and with societal attitudes toward contraception changing, the fertility rate dropped sharply and stabilised at around the population replacement level of two children per woman in the early 21st century. By 2017 it had fallen below two children per woman of childbearing age.