S&P 500 Long-term Price Chart (1905 - Present)
Here is a chart of inflation-adjusted monthly closing prices for the S&P 500 from 1905 to now. Price data from ONLINE DATA ROBERT SHILLER. The chart shows several complete price cycles plus the upside and fledging downside of the current cycle that is now in the making. The black upward-sloping line is the long-term trendline of prices as computed using the standard liner regression model.
What's scary about the chart is the distance between the current price and its corresponding trendline price. In previous price cycles prices rose above the trendline for many months, fell back to the trendline and even fell below it. This reversion to the mean is present in many stock price charts.
If a reversion happens for the downside of the current price cycle, prices would drop dramatically from current levels.
Current S&P 500 value of 4,594.63 is 89.47% from the trendline.
S&P 1971 - Present   S&P 1982 - Present   NASDAQ Composite Index 1971 - Present