Books using words indicating sadness, shown here on the red literary misery line, correlated to, with about a ten year delay, economic misery, which is shown on the black line. In other words, the more miserable the economy at the time, the sadder the books written a decade later. This gap is attributed to the fact that authors either grow up during a recession and then write about it when they become adults, or that writers in general use the past decade, roughly, to draw from. Economic misery was counted by the sum of inflation and unemployment.
–from PLoS One and The Guardian