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Market Crashes...A Bad Omen or Time to Buy?

So the Dow lost a whopping 512.76 points Thursday.  Is this a signal of pending doom or can we expect some reversion to the mean?  Despite the ugliness of today, this type of downward movement is not rare.  In fact, on percentage terms, since 1928, there have been 103 days where the Dow's daily drop has been worse than today.  I decided to do a little research on how the market reacts to such days, looking at percentage gain or loss the next day, 5 days out, 30 days out, and 250 days out. 

Here are the results:

1 Day:        +0.07%
5 Days:      +0.31%
30 Days:    +1.11%
250 Days:  +7.57%

Seeing as the 250 day number is pretty close to the long term annual average gain of the stock market, it's hard to really answer the question initially posed.  

However, if we use the median returns instead of average returns, we get:

1 Day:        +0.07%
5 Days:      +0.11%
30 Days:    +1.73%
250 Days:  +2.95%

Although the returns are still positive, they show positive skewness towards a more moderate return.

To see the whole range, here are the maximum gains and losses:

Maximum Gains:

1 Day:        +14.87%
5 Days:      +23.80%
30 Days:    +62.47%
250 Days:  +159.91%

Maximum Losses:

1 Day:        -22.61%
5 Day:        -18.60%
30 Days:    -26.47%
250 Days:  -69.79%

Since the data set I used consisted of 103 points WORSE than today, I wondered what the results would be if I used an identical sample size, but chose the 103 down days most similar to today (percentage-wise).  Results were very comparable to what is presented above, so I won't post them.

So what did you do today?  Jump ship, or load up?

Disclosure: I have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours.