Similarly, the Nikkei took about 2 years to fall past its 50% point, dropping over 80% total, then almost returned to the 50% level within 17 years, but the current crisis prevented a return to high-water mark levels: 
More than that, TA is useless when so many stocks in the index(es) are being kept in the index in violation of prior criteria for inclusion and retention.
eg, there are five stocks now in the DJIA that should be replaced - AA, BAC, C, GE and GM.
The SP500 has dozens of stocks that no longer meet the capitalization requirements for inclusion - and they’re still in there.
The best we can do is simply look at price levels relative to prior lows and volume. Chart patterns on indexes are broken. TA on any banking or finance stock is rendered useless by exogenous events in the credit markets and Washington DC.
One set of chart patterns that ARE useful are the patterns from 1930. The only difference between now and then is that we’ve gone down harder, faster, than the market did in 1929/1930 - but those charts show how the market makes small, 10 to 20% counter-trend rallies on the way down.
Similarly, the Nikkei took about 2 years to fall past its 50% point, dropping over 80% total, then almost returned to the 50% level within 17 years, but the current crisis prevented a return to high-water mark levels:
