A bull market is a period in which stock prices are rising or are expected to rise, typically defined as a 20% or greater increase from a recent low point. Bull markets are characterized by investor optimism, increased buying activity, and positive economic indicators such as rising GDP, low unemployment, and strong corporate earnings. They can last for months or even years. The longest bull market in US history ran from March 2009 to February 2020, lasting nearly 11 years and seeing the S&P 500 rise over 400%. During bull markets, trading volumes tend to be higher as more investors participate, and IPO activity increases as companies take advantage of favorable valuations. Understanding whether you're in a bull market helps inform investment strategies, as momentum-based and growth-oriented approaches tend to perform better during sustained uptrends. However, bull markets don't rise in a straight line and can include significant corrections of 10% or more.