What's somewhat interesting is that at both very low and very high income levels, the % of stay-at-home parent is higher. So for people near poverty, or people making top 1%-ish income, it's less than a 2:1 ratio, more like 35-40%. For middle income like $40k-$100k, it's more like 3:1 or 4:1.
At no income level is it lower than 20% stay at home parent though, so not too much of an outlier in any case.
Not much of an outlier.