Chances that tomorrow will be up/down based on prior days up/down

This is been discussed in other blogs.  The question is: given the market has been down/up x days in a row, what are the chances that tomorrow will close higher (up day) or lower (down day) than the previous day’s close?  For up days, I start with a down day, and then count the number of consecutive up days.  Reverse for down days.  I ignore strings with no change.  The results indicate that until you get to around 5 days in a row, the odds are about 50-50, with the likelihood of reversing direction slightly better if the string direction is down. Here are the results looking at SPY since 1999.  Remember that a down_up_up day counts are included in the down_up day counts, so the difference between those two patterns is the number of times the other direction (down_up_down) happened.

pattern # of times % continuing
down_up 691
down_up_up 352 51%
down_up_up_up 189 54%
down_up_up_up_up 96 51%
down_up_up_up_up_up 46 48%
down_up_up_up_up_up_up 20 43%
up_down 688
up_down_down 333 48%
up_down_down_down 158 47%
up_down_down_down_down 67 42%
up_down_down_down_down_down 26 39%
up_down_down_down_down_down_down 8 31%

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