America is teeming with Wal-Marts, Home Depots and other “big-box” chain stores — some larger than five football fields. Millions of consumers like the low prices, free parking and one-stop shopping convenience offered by the megastores, while policymakers say the stores create jobs, enable customers to save money for other expenditures and pump much-needed tax dollars into community coffers. But critics say big-box stores actually harm local economies and flourish only because they receive public subsidies, pay low salaries and benefits and utilize unethical and possibly illegal practices to drive smaller, locally owned competitors out of business. Critics also say they cause added traffic congestion and suburban sprawl, force U.S. companies to ship high-paying manufacturing jobs overseas and cost more in local services than the taxes they generate. Communities increasingly are passing special ordinances to keep the big retailers out, but the chains are fighting back, saying they are simply giving consumers what they want.