shares of carmax inc kmx shed 223 to 8843 tuesday on what proved to be an allaround rough trading session for the stock market with the sp 500 index spx falling 281 to 417520 and dow jones industrial average djia falling 238 to 3324018 carmax inc closed 6755 short of its 52week high 15598 which the company reached on november 8th the stock demonstrated a mixed performance when compared to some of its competitors tuesday as copart inc cprt fell 347 to 11411 autonation inc an rose 050 to 11615 and penske automotive group inc pag fell 125 to 9922 trading volume 15 m remained 353577 below its 50day average volume of 18 m editors note this story was autogenerated by automated insights an automation technology provider using data from dow jones and factset see our market data terms of use