Stock-Callers.com spotlighted auto dealership groups in its recent stock research report.It stated the auto dealership industry, which continues to benefit from an improved labor force, cheap gas and low interest rates. The firm reviewed CarMax Inc., AutoNation Inc., Penske Automotive Group Inc. and Copart Inc.Richmond, Va.-based CarMax Inc.'s shares rose 1.6 percent and finished the Aug. 15 trading session at $60.51. A total volume of 1.45 million shares was traded. In the last month and the previous three months, the stock has advanced 9.56 percent and 19.49 percent, respectively. Additionally, the company's shares have gained 12.12 percent since the start of this year. The stock is trading above its 50-day and 200-day moving averages by 13.61 percent and 16.45 percent, respectively. AutoNation Inc., Fort Lauderdale, Fla., recorded a trading volume of 1.68 million shares on Aug. 15, above its three months average volume of 1.21 million shares. The stock ended the session 0.86 percent higher at $49.26. The company's shares have gained 5.55 percent in the previous three monthsPenske Automotive Group Inc., headquartered in Bloomfield Hills, Mich., closed recently at $42.84, climbing 3.78 percent. The stock recorded a trading volume of 1.56 million shares, which was above its three months average volume of 772,570 shares. The company's shares have gained 24.26 percent in the last month and 19.14 percent in the previous three months. At the closing bell Aug. 15, shares in Dallas-headquartered Copart Inc. ended 0.43 percent higher at $50.84 and with a total volume of 346,646 shares traded. The stock has advanced 1.88 percent in the last month and 16.98 percent in the previous three months.