In the 80s mortgage rates hit 20%. So there's a start. Wages weren't quite as skewed to the high end as they are today. The gap between low middle, middle, and upper middle was not as wide, so it was less likely to hit the threshold for the 70% bracket. There were far more single income families, so again, not as likely to hit the threshold. Finally it's a marginal rate. Only income above the threshold would be taxed that much, not one's entire income.