Each business day, TheStreet.com Ratings compiles a list of the top five stocks in one of five categories -- fast-growth, all-around value, large-cap, mid-cap and small-cap -- based on data from the close of the previous trading session. Today we focus on mid-caps. These are stocks of companies that have market capitalizations of $500 million to $10 billion that rank near the top of all stocks rated by our proprietary quantitative model, which looks at more than 60 factors.The stocks must also be followed by at least one financial analyst who posts estimates on the Institutional Brokers' Estimate System. They are ordered by their potential to appreciate. Note that no provision is made for off-balance-sheet assets such as unrealized appreciation/depreciation of investments, market value of real estate or contingent liabilities that might affect book value. This could be material for some companies with large underfunded pension plans. Pegasystems' ( PEGA) business management software helps companies manage complex, changing business processes by automating decision-making and the implementation of those decisions. We have rated the company a buy since May 2008. This rating is based on the company's growth, solvency, and expanding profit margins. For the fourth quarter of fiscal 2008, the company reported revenue growth of 26.9% year over year. Continuing an impressive record of earnings-per-share growth, Pegasystems' EPS improved significantly, rising from 3 cents to 8 cents. Net income also increased in the fourth quarter, surging 99.6% from $1.4 million to $2.8 million. Both revenue and net income growth exceeded the averages for the Software industry. Pegasystems' gross profit margin is rather high at 64.8%; it has increased from the same quarter a year ago. The company has no debt to speak of, and its resulting debt-to-equity of zero can be seen as a favorable sign. In addition, Pegasystems maintains a quick ratio of 3.4, which clearly demonstrates its ability to cover short-term cash needs.