How much of this change is simply the result of the rise in women joining the work force? Given that something like the female labor force participation rate is

How much of this change is simply the result of the rise in women joining the work force? Given that something like the female labor force participation rate is some 20% higher now than in the 70s, it seems likely to me that most of the change reflects the rise in two-earner households and the decline in family sizes.