Chinese investors, including some from Hong Kong, have bought property near drilling rigs in the northern United States to share in the country's oil boom. Robert Gavin, chief executive of North Dakota Developments, said the investors were attracted to his company's hotel suites in North Dakota because projected gross rental yields were 46 per cent per year, which would be made possible by low purchase costs, expected high occupancy levels of more than 90 per cent, and "substantive nightly rates" of US$139. The suites are rented out to visiting oil executives. Thousands of oil workers are moving to North Dakota. Developers building accommodation for them include North Dakota Developments, which will complete construction of the first two phases of the Great American Lodge hotel for visiting oil company employees in the town of Williston next month. North Dakota Developments is marketing 440 hotel suites for sale to investors in the first two phases at Great American Lodge, with 80 sold to mainland Chinese buyers and 15 to Hong Kong investors. Prices start from US$49,590 for a guest room with en-suite toilet and shower room. Recent advances made in hydraulic fracturing technology, also known as fracking, a process that releases oil and gas deposits in shale, has opened up an oil field in the Bakken region which straddles the US-Canadian border. Oil production in North Dakota, where most fracking is taking place, has risen tenfold from 2.5 million barrels per month in 2009 to 25 million barrels per month last year, according to the US Energy Information Administration. Residential schemes in the area include a project by private equity fund KKR to build 1,000 homes in Williston, but housing demand far outstrips supply in North Dakota. Jeffrey Baker, managing director at Savills, a property consultancy which has been advising institutions on property investment in North Dakota, said housebuilders could not keep up with demand because workers preferred to be employed in the oil industry, where wages were higher than in construction. A developer entering the market had to bring in workers from outside and provide temporary housing for them, and that was delaying construction of new homes, he said. "Activity in North Dakota is staggering in terms of population explosion and demand," Baker said. "It is like the 'wild West', with 15,000 housing units needed in Bakken to house oil industry employees who are living in cars, crew camps and offices." Housing demand will grow stronger, because the oil industry is projected to expand sixfold over the next 23 years. According to North Dakota State University the number of Bakken oil wells may increase by 39,678 to 46,187 by 2036.