An economist called Robert Shiller wanted to come up with a way of comparing valuations based on price/earnings ratios but without the distorting effect of the economic cycle on what the earnings were.
He devised a metric – the cyclically-adjusted price to earnings ratio (CAPE). This averages 10-years of earnings (adjusting for the effects of inflation) to come up with an “earnings” number. That should, in theory, strip out the effect of the cycle.