Dow all time high on no volume. http://finance.yahoo.com/echarts?s=%5EDJI+Interactive#symbol=^dji;range=1y;compare=;indicator=volume;charttype=area;crosshair=on;ohlcvalues=0;logscale=off;source=undefined; Friday SP500 ATH on decreased volume. http://finance.yahoo.com/q/hp?s=%5EGSPC+Historical+Prices Not sure about the volume today, and will be posted later. Is this holiday light already? Could explain it, if all the small fries buy into the market when they are home on holiday, while all the big bucks are having a real holiday.