When and if the 50-day average falls below the 200-day average, as it one day will, the case for bullish optimism will suffer. There's nothing magical about 50 and 200 day averages, of course. We could just as easily focus on, say, 61- and 197-day averages and suffer no less authority on matters of the market's technical profile. But the fact that the 50- and 200-day averages are widely followed suggests that a death cross by this definition could resonate on a deeper level with the crowd when it strikes.