Within this country’s most populous, developed cities, a disturbing trend is emerging as middle class families are being forced out due to the struggle of income inequality and affordable housing.

According to a study produced by residential real estate magnet, Trulia, among the United States’ 100 largest metros, nearly 63 percent of homes can be categorized as affordable for the middle class. However, when you look solely at the nation’s top-20 metros, the percentage of affordable housing is cut by nearly one-fourth. Within these metros the trend is quite clear: even when considering that middle class families in richer cities have a higher level of total income, housing affordability falls as household income rises.

Trulia economist, Jed Kolko, breaks it down even further, noting that middle class families in liberal cities seem to suffer on the more extreme end of this affordability crisis. “Even after adjusting for differences in income, liberal markets tend to have higher income inequality and worse affordability,” Kolko said.

Why does it seem that liberal cities are more averse to affordable housing for the middle class? It’s possibly a result of a failure to look at the larger picture. A combination of historical preservation, support for higher taxes, rent control measures, and overzealous government-based housing regulations equates to communities that simply become so enveloped in regulations that they force the middle class out.

Change is needed throughout this country, and in developed cities in particular, to ensure that the backbone of this nation—the middle class—can afford to work, live, and raise a family. The often overbearing reach of local government could stand to be rethought and re-worked so that the average American consumer is not, quite literally, left out in the cold.