[Ralph F. Keeling et al., Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis] (scientificamerican.com)
Put another way, stock prices grew faster than earnings, meaning that PE ratios, what investors were willing to pay for a dollar of earnings, had a long - term secular increase over the period. (badmoneyadvice.com)
The borehole reconstruction (bold red) shows a striking secular increase since 1500. (judithcurry.com)