Property & casualty insurance insures against loss to property due to weather events or man-made disasters and accidents. It is necessary for anyone - individuals and businesses, who own property. The insurance industry contributes 4-and-a-half-percent of GDP, of which 74% is provided by insurance carriers that underwrite insurance, and 26% by insurance agencies that sell insurance to the public. The insurance sector has grown faster than GDP in the last 17 years, and the premiums have grown less than inflation, which in an indication that the business is very competitive. Let's take a look at some of the best property & casualty insurance companies TheStreet Quant Ratings says you should add to your portfolio, immediately. Number 3 is Allstate. With an 'A+' rating, the company's strengths can be seen in its revenue growth and solid stock price performance. 2nd is, The Travelers Companies. This rating is an 'A+.' The Travelers Companies thrives in its attractive valuation levels and solid stock price performance. Number 1 is ACE Limited. With an 'A+' rating the company flourishes in its largely solid financial position with reasonable debt levels by most measures and increase in stock price during the past year. TheStreet Ratings are algorithmic stock picks based on 32 major data points. S&P 500 stocks rated 'buy' yielded a 16-and-a-half-percent return in 2014, beating the S&P 500 Total Return Index by more than 300 basis points. For the full reports on these stocks, you can check out TheStreet.com/QuantRatings.