The middle of The 20th Century was marked by a significant and persistent increase in fertility rates in many countries of the world, especially in the Western world. The term baby boom is often used to refer to this boom, considered to have started immediately after World War II, although some demographers place it earlier or during the war. This terminology led to those born during this baby boom being nicknamed the baby boomer generation.
The boom coincided with a marriage boom. The increase in fertility was driven primarily by a decrease in childlessness and an increase in parity progression to a second child. In most Western countries, progression to a third child and beyond declined, which, coupled with an increase in transition to first and second child, resulted in higher homogeneity in family sizes. The baby boom was most prominent among educated and economically active women.
The baby boom ended with a significant decline in fertility rates in The '60s and The '70s, later called the baby bust by demographers. In the United Sates, the boom corresponds to the birth years of 1946 to 1964.
