In the “decades” timeframe, the current Secular Bull Market could turn out to be among the shorter Secular Bull markets on record. This is because of the long-term valuation of the market which, after nine years, has reached the upper end of its normal range.
The long-term valuation of the market is commonly measured by the Cyclically Adjusted Price to Earnings ratio, or “CAPE”, which smooths out shorter-term earnings swings in order to get a longer-term assessment of market valuation. A CAPE level of 30 is considered to be the upper end of the normal range, and the level at which further PE-ratio expansion comes to a halt (meaning that increases in market prices only occur in a general response to earnings increases, instead of rising “just because”).