TSC Ratings provides exclusive stock, ETF and mutual fund ratings and commentary based on award-winning, proprietary tools. Its "safety first" approach to investing aims to reduce risk while seeking solid outperformance on a total return basis.You can count on one hand the number of industries whose shares have fared worse than insurance companies' in the past six months. But not all insurers are in the same position -- some have been unfairly punished and are trading at tempting values. The companies vary in size, from a market value of $16 million for Security National Financial ( SNFCA) to Loews ( L), which has a market value of $9.6 billion. The life and health insurance index of the S&P 500 has fallen 56% over six months, more than twice as much as the benchmark. It's ranked 150th of 154 industry groups on the S&P 500. Property and casualty insurers have done better, dropping 23% -- in line with the S&P 500 -- during the past half year. Coventry Health Care ( CVH), whose stock has fallen 68% from a year earlier, has a price-to-book value of 56%. A company's book value is its total assets minus intangible assets and liabilities. The higher the percentage, the more fairly valued a company is. Unum Group ( UNM) is down 43% and is trading at 65% of book value. Assurant ( AIZ) has tumbled 64% and trading at 69% of book value. The insurer with the lowest price to book is Security National Financial, at 26%. Aside from price to book, other inexpensive stocks are Loews, which has a trailing price-to-earnings multiple of only 2.4. HealthSpring's ( HS) return on average assets is 8.4%. TheStreet.com Ratings has compiled a list of 10 stocks trading at a substantial discount to book value.