Good comment by Arther Hill

The S&P 500 ETF (SPY) has been trading between 110 and 123 since early August (seven weeks). During this timeframe, the ETF has crossed the midpoint (116.50) at least 11 times. There have also been nine swings of at least five percent. This is more than one swing per week! Such a volatile consolidation is not enough to affect medium-term trend, which is down after the August breakdown. However, it is producing sizable short-term swings. The only way to make money short-term is to buy immediately after the upturn and sell the immediately after the downturn. Sometimes chartists can use a trendline or support/resistance level to identify a short-term reversal.