Until the early 1950s construction remained in the hands of small domestic companies. Increased income from oil and gas and easy credit triggered a building boom that attracted international construction firms to the country. This growth continued until the mid-1970s when a sharp rise in inflation and a credit squeeze collapsed the boom. The construction industry had revived somewhat by the mid-1980s, although housing shortages and speculation remained serious problems, especially in large urban centers. As of January 2011, the banking sector, particularly Bank Maskan, had loaned up to 102 trillion rials ($10.2 billion) to applicants of Mehr housing scheme. Construction is one of the most important sectors accounting for 20–50% of total private investment in urban areas and was one of the prime investment targets of well-off Iranians.