Purpose: News flow continuously, events happen regardless markets' schedule; For example, markets digest '1 day information from Tuesday to Friday; On Monday markets have to chew up 3 days information (Saturday, Sunday, and Monday); As such, price movements on Monday must be bigger than other weekdays, is my idea. Method: to see this I go over S&P 500 index from 1970; Sort daily (business day) close price change into groups by calendar day difference; calculate average, and standard deviation for each group. Results: Below figure shows the summary; Standard deviation increased along with number of days up to 3. In date-wise, 2 days standard deviation should be square root of 2 times bigger than 1 days deviation, but not that much (1.09% to 1.03%, 1.06 x); and 3 days should be square root of 3 times bigger, but the results were 1.25% to 1.03%, 1.21; There are less events and economic news may be behind this; below is the chart for standard deviation. Average index change va...