A man works on the rig of an oil drilling pump site in McKenzie County outside of Williston, North Dakota March 12, 2013. North Dakota's booming oil business has quickly ran up against a serious shortage of housing for the thousands of workers who have poured into the state looking to cash in on the Bakken oil formation that has made North Dakota the second-largest oil-producing state after Texas. Picture taken on March 12, 2013. REUTERS/Shannon Stapleton (UNITED STATES - Tags: BUSINESS ENERGY ENVIRONMENT COMMODITIES)