Market trends seldom take place in straight lines. Most trend pictures show a series of zig-zags with several corrections against the existing trend. These corrections usually fall into certain predictable percentage parameters. The best-known example of this is the fifty-percent retracement. That is to say, a secondary, or intermediate, correction against a major uptrend often retraces about half of the prior uptrend before the bull trend is again resumed. Bear market bounces often recover about half of the prior downtrend. A minimum retracement is usually about a third of the prior trend. The two-thirds point is considered the maximum retracement that is allowed if the prior trend is going to resume. A retracement beyond the two-thirds point usually warns of a trend reversal in progress. Chartists also place importance on retracements of 38% and 62% which are called Fibonacci retracements.