Wade - hypothetically if it were true that stocks went down an average of 2% after posting earning, then it would be easy money for computer algorithms and day traders. Short the day before and buy back the next day at an average 2% lower .... BUT in the process of exploiting a market inefficiency like that, it would quickly disappear. The same logic applies to buying the day before ex-dividend to collect the dividend and selling the next day. Of course the stocks go down by the amount of the dividend on average ..... otherwise it would be free money for day traders to exploit.
Most of my stocks are long term holds .... such as my largest sector weighting in the homebuilders. I always hold those through earnings. They almost never disappoint. Same goes for stocks like AER, HALO, CUBI, BLDR, KOP, etc. I always hold through earnings, aside for a bit of short term trading around a much larger core position, those are long term holds. That gets me a much lower tax rate and defers the taxes until I sell. I intend the same for RMAX ..... that's a long term play on a sector rebound, not short term.
Riskier plays like AAOI that have run up partly on hype.... yes a good idea to sell ahead of the numbers. Or a stock like BELFB that had too big a run and looks ripe for a fall as Hweb pointed out. For those types of situations I sell at least part of my position before the report.
