Hundreds of people protested at a suburban Maryland Wal-Mart over wages and worker protections Thursday as D.C. Mayor Vincent C. Gray (D) weighed whether to sign legislation that would force the nation's largest retailer to pay a 50 percent premium over the city's minimum wage.

Nothing's ever as simple as we'd like it to be. A case in point: Policies that simply increase access to supermarkets may not get people to choose an apple over ice cream, a recent study reported. Changing people's eating habits is difficult, in other words.