Both NYSE and ES (e-mini S&P futures) volumes were the lowest of the year so far. This is the lowest non-holiday trading day on the NYSEVOL (from Bloomberg) since its data began a decade ago and eyeballing ES volumes, this appears to be one of the lowest ever volumes of the last few years. For those who think this is irrelevant as the market's price has risen and so total USD volume remains approximately equal - wrong! Today is the lowest USD volume day since the mid 2009 (which tended to coincide with holiday trading volumes around July 4th) - making today's USD trading volume less than 50% of their 2004-2007 average!

A proxy for total USD trading volume - NYSE Volume multiplied by the S&P 500 is at decade low levels for a non-holiday period...

and NYSE Volume standalone...

Charts: Bloomberg