You can see that the 2000 top of the dotcom bubble began what so far is a 12 year trading range. Such ranges are common after extended bull markets like the 1982-2000 bull market. For instance, the 1949-1966 bull market was followed by a 16 year trading range from 1966 to 1982. Similarly, the 8 year bull market of the1920's was followed by a 13 or 20 year trading range (depending on how you measure it).
What happens in these instances is that during the trading range the market gradually moves from a very over-valued condition to a very under-valued condition. This takes a lot of time, but at each successive bear market low within the trading range you can see price-earnings ratios lower than at the preceding bear market low and dividend yields higher.
So far within the current range there have been two bear market lows - one in 2002 and the second in 2009. At the 2009 low the Dow and the S&P were definitely under-valued by standard measures but not nearly so much as in 1982 or in 1949. This is one reason why I think that there will be at least one more bear market of consequence before the major averages move out of the current trading range to the upside in a decisive way. In the mean time I think the obvious spot to be watching for a bull market top and the start of the next bear market is in the vicinity of the 2000 and 2007 tops (red dash lines). These tops were at 1553 and 1576 respectively, so the S&P has about 8% to go on the upside before reaching them.
A break below the green dash trend line would probably meant that the next bear market is underway.
When might a low comparable to 1982 or 1949 develop? Answers to such timing questions cannot be more than educated guesses. The 1949 low occurred 20 years after the 1929 top. That makes 2020 one reasonable guess for the final bear market low of the trading. It is worth noting that George Lindsay's 12 year period from major high to major low ends in 2019-2020 if counted from the 2007 top. On the other hand, the 1982 low occurred 16 years after the 1966 top. That makes 2016 a second guess. That year is 12 years from the 2004 intermediate term top which was followed by a multi-month correction so there is a Lindsay time period pointing to a low in 2016 too.
No matter how you look at it - valuations or timing - the odds are that there will be at least one more bear market before this long trading range ends and probably two more. So long term investors should be watching the market carefully as it moves toward the red dash lines on the chart above for signs that the current bull market is about to end.