UNITED STATES — The housing crunch has been well documented in high-cost big cities, where rents and mortgages break the bank. Now it has moved into the rest of the country. The culprit is too little housing, and it began two decades ago. …Cities and states understand they have a housing problem. To increase the pace of construction, many have cut back regulatory barriers that make housing slow and expensive to build. …But the nation’s housing shortage isn’t only about zoning in cities. For one thing, developers everywhere find it harder to raise money, and homeowners find it harder to get loans. That’s because banks and the government, in a quest to prevent another housing bubble, have raised lending standards and made mortgages harder to get. For another, builders simply aren’t putting up subdivisions at the rate they once did. [to access the full story a NY Times subscription is required]