NEW YORK ( TheStreet) -- Sonic Corporation (Nasdaq: SONC) is trading at unusually high volume Thursday with 1.8 million shares changing hands. It is currently at 4.2 times its average daily volume and trading down 57 cents (-7.2%) at $7.40 as of 3:50 p.m. ET. Sonic has a market cap of $406.9 million and is part of the services sector and leisure industry. Shares are up 18.4% year to date as of the close of trading on Wednesday. Sonic Corp. operates and franchises a chain of quick-service drive-in restaurants in the United States. As of October 03, 2011, the company operated and franchised approximately 3,500 drive-ins. It also leases signs and real estate. The company has a P/E ratio of 28.2, above the average leisure industry P/E ratio of 19.2 and above the S&P 500 P/E ratio of 17.7. TheStreet Ratings rates Sonic as a hold. Among the primary strengths of the company is its respectable return on equity which we feel is likely to continue. At the same time, however, we also find weaknesses including deteriorating net income, poor profit margins and weak operating cash flow. You can view the full Sonic Ratings Report. See all heavy volume stocks in our stocks moving on unusual volume list or get investment ideas from our investment research center. Interested in other stocks that are falling on unusually high volume? Get free SMS text alerts sent to you when the action happens by texting HVDOWN to 95370 or select from multiple alert options.