Volume analysis
Date Open High Low Close Volume Adj Close*
Dec 18, 2014 2,018.98 2,061.23 2,018.98 2,061.23* 4,703,380,000 2,061.23
Dec 17, 2014 1,973.77 2,016.75 1,973.77 2,012.89* 4,912,370,000 2,012.89
Dec 16, 2014 1,986.71 2,016.89 1,972.56 1,972.74** 4,958,680,000 1,972.74
Dec 15, 2014 2,005.03 2,018.69 1,982.26 1,989.63** 4,361,990,000 1,989.63
Dec 12, 2014 2,030.36 2,032.25 2,002.33 2,002.33 4,157,650,000 2,002.33
*Up on lower volume
**Down on higher volume
http://finance.yahoo.com/q/hp?s=%5EGSPC+Historical+Prices