Radian Group (RDN) saw its delinquent mortgage inventory fall from 111,434 loans at the beginning of July to 110,607 at the end of the month. Meanwhile, the mortgage insurer wrote $1 billion in new business last month. Last week, the company reported second-quarter income of $137.1 million, or $1.03 a share, buoyed by changes in the fair value of derivatives and other financial instruments. For the year-ago quarter, Radian reported a loss of $475.1 million, or $4.31 a share, due to the value of derivatives that swung in a negative direction, eating into profits. In July, nearly 8,100 loans insured by Radian moved into delinquency, while 5,820 were cured and 2,430 were paid. The Philadelphia-based firm faced a tough week on Wall Street, with mortgage insurance stocks plummeting as much as 20% after Standard & Poor’s lowered the nation’s debt rating. Radian’s stock was trading down nearly 30% Monday to a new 52-week low before bouncing back somewhat before close. Write to: Kerri Panchuk.