WASHINGTON (MarketWatch) - Construction of new U.S. homes sank 11.7% to an annualized rate of 519,000 in October, the lowest level in 18 months, but permits rose slightly, the Commerce Department reported Wednesday. The last time starts were that low was in April 2009. In addition, housing starts in September were revised down to 588,000 from an original reading of 600,000. Economists surveyed by MarketWatch had expected housing starts in October to drop to an annual rate of 600,000 on a seasonally adjusted basis. Permits for new construction, viewed as a more accurate gauge of home building, rose 0.5% in October to an annualized rate of 547,000. Permits were also revised slightly higher in the prior month.