When was the slogan "One is not enough, two are just right, and three are more"?

1973 the policy put forward by the state is "late, rare and young" ("late" means that men get married at the age of 25 and women get married at the age of 23; "Sparse" refers to lengthening the birth interval, and the interval between two births is about 4 years; "Less" means having only two children). It quickly evolved into "more than one, two just right, more than three." In 1978, the state further clearly put forward the policy of "promoting a couple to have the best number of children, with a maximum of two children".