It's pretty much impossible to support a family on one income these days, due to healthcare costs, even if you live as frugally as people did decades ago. Healthcare used to cost only a fraction of what it does now. I have some friends who try to support their wife and kids with their income alone, but literally half their paychecks go to just paying for healthcare/doctor's visits/hospital bills/etc. With food prices at all time high, rent skyrocketing in many areas, daycare costs being as ridiculous as they are, the only way you stand a chance of supporting a family comfortably on one income is if you make at least $60k, and that's only if you live in a cheap area.
See this article, and see the chart for median household income adjusted for inflation. Notice how it has remained fairly stagnant over the decades (except for the richest people of course). Now take into account the huge rise in healthcare costs over the years, and people have less and less disposable income.
http://www.advisorperspectives.com/d...stribution.php