Several weeks ago Citigroup announced their intention to undergo a 1 for 10 reverse stock split. The ex-date on the rerverse split is not yet determined, but the implications on total market volume should not be ignored. The technical folks like to point to market volumes as a signal indicating the importance of market advances and declines, but do not be alarmed if there is a sudden contraction in trading volume after Citi's share price jumps from $4 to $40.
The chart below shows Citi's daily volume as a percent of total NYSE volume. In a special note to paying customers, Birinyi Associates detailed that - all things being equal - Cit's reverse split will cause total NYSE daily volume to decline by about 11%. Although we still do not know the exact dates, be wary volume as an indicative measure.