NEW YORK ( TheStreet) -- MetLife ( MET) was upgraded by TheStreet Ratings to a buy from a hold on Monday and is undervalued compared to its peers. MetLife has an estimated price-to-earnings ratio for next year of 7.41. The average for life insurance companies is 13.05. Aflac ( AFL) and Assurant ( AIZ) also have low forward P/Es of 7.03 and 6.79, respectively. Of the 23 analysts who cover MetLife, 18 consider it a buy; five rate it a hold. Shares of MetLife hit a 52-week high a year ago of $48.72. The stock's 52-week low of $25.61 was set on Oct. 4. The stock has risen 20.69% year to date to $37.63, its closing price on Friday. TheStreet Ratings gives MetLife a B- grade with a $42.02 price target. "We first wrote about the disconnect between share prices and CDS spreads in September (Disconnect between MET/PRU valuations & CDS a bullish sign, 08 September 2011) and we believe that the trading opportunity remains in place today," Bank of America Merrill Lynch analysts wrote in a Jan. 30 report. "Since the beginning of the financial crisis, CDS spreads have explained between 50%-60% of life insurance P/BV multiples. We believe that this relationship should be much less significant over the long term. However, even in the current, CDS-driven environment (i.e., excessive concern about tail risk), implied valuations based on CDS suggest that LNC should be at least 30% higher today and MET should be 20% higher."