Private mortgage insurance activity slowed in the third quarter, but the drop in mortgage refinance volume clearly had less of an impact on the MI industry than it had on lenders. Private MI earnings on U.S. mortgage insurance activity declined 7.4 percent from the second quarter, to $475.2 million, according to an Inside Mortgage Profitability analysis. On a year-to-date basis, the $1.48 billion in income reported by the seven companies was off 3.9 percent from…