For more coverage from TheStreet.com Ratings team, check out TheStreet.com Ratings section.Our models rate Abbott Laboratories ( ABT) an A+, a grade from TheStreet.com Ratings that corresponds to a buy rating. Abbott's shares are up just about 2.5% year to date, and the drug company just completed another quarter of double-digit profit growth driven by sales of its Humira arthritis medicine and new Xience drug-coated stent. Other strengths of the company include its low risk of patent expiration concerns, diversified product lines and the non-discretionary nature of its products. These strengths definitely bode well for the company as the economy enters a downturn. In 2001 and 2002, during the last economic downturn, Abbott Labs hardly noticed it and did not miss a beat in terms of its sales and earnings growth. But what is Abbott's stock roughly worth? The company's financial statements and earnings calls, which are available on the Web, offer some clues. The most notable aspect of the company's balance sheet is its retained profits totaling $10.8 billion, which has essentially funded a quarter of the company's asset base of $39 billion. The key point is that its book value, asset base and its retained profits have all been growing at roughly the same rate -- 13.9%, 13.5% and 10.6%, respectively -- over the past 10 years.