I'll get to the rest of it later, because I'm not really committed to my 'thesis', it's just a thought I've wondered about, and you might have a convincing alternative explanation. But this bit here I don't find exactly conclusive. When something was 'invented' has little to do with when it became widely available as a mass-market consumer product, and those dates you give are perfectly consistent with my suggested theory. It takes time for material changes to change behaviours. There were a large number of material inventions that gradually reduced the need for full-time labour to maintain the domestic sphere, over the course of the 20th century. Again, though, I'm not really wedded to this theory, it might not be the explanation for what's happened.
I don't really understand this part. I meant 'as a proportion of the population'. As in the '50s or before, most women didn't have paid employment outside the home, how can it be that the available workforce is now only 10% larger than then? By making paid employment the norm for women, has that not doubled the available workforce? If it's only gone up by 10%, where has the rest of it gone?
More students (due to a longer duration of education now required)? Earlier retirement? Or, very possibly, I am just underestimating the number of women who _did_ have paid employment, even in earlier eras? (Black and working-class women have always worked, as has been pointed out a few times to earlier generations of white feminists...but then maybe one could argue the effect of the devaluing of labour is only on the slightly-better-off classes, i.e middle-class white families?)
OK, you have actual figures here, which do seem to support your argument. But I'm puzzled by those figures. As you say, it does depend very much on how one defines a 'job'.