Why are there so many baby boomers?

It is my understanding that the "baby boom" resulted from the return of millions of young American men (and women) from World War II. Having been away from the US for as many as 4-5 years, the returning GIs immediately sought out their girl friends (or wives), married them (novel idea, no?) and proceed to produce babies in record numbers. The US economy was booming after the war, and there was a huge spike in the number of babies born in this country. These babies - born starting in 1946 and lasting thru 1964 - are known as the "baby boom", hence "baby boomers".