A bull market is a sustained upward trend in asset prices, conventionally defined as a rise of at least 20% from a recent low. Bull markets are associated with economic expansion, rising corporate earnings, low unemployment, and broad investor optimism. The longest bull markets in equity history have run for years, rewarding buy-and-hold investors who stayed committed throughout.
For market timers, bull markets present a specific challenge: trend-following strategies tend to work well in bull markets, but the very nature of a long, sustained uptrend means that any exit — even a well-intentioned one — risks missing a significant portion of the recovery if the re-entry is delayed. Many timing strategies underperform buy-and-hold across full bull-market cycles precisely because they exit too early and re-enter too late.
Bull markets do not move in straight lines: they include corrections (10–20% declines) and periodic volatility spikes that can trigger timing signals even while the secular trend remains up. Distinguishing a correction within a bull market from the start of a genuine bear market is one of the hardest problems in applied market timing.