That's probably one of the caveats and addenda. So, my counterargument doesn't prove that life has gotten better--maybe an additional kid is "better" than six hours of leisure time by some calculuses. But it does rebut any argument that we used to get by one 40 hours per week per household of labor but now we need 80.

Edit: Of course, as parent notes the drop in number of children represents at most _part_ of the increase in leisure hours. We can definitely attribute part of it to things that are definitely modern advantages, like labor-saving devices such as dish-washing machines. The year 1965 is kind of a poor year for my argument, in that by that point most households had the most labor-saving devices: refrigerators that allow you to shop and cook days at a time, washing machines that saved many hours of labor washing clothes, etc.