People have given good responses here, but the other, important reason is because when people in the lower socioeconomic strata make more money, they’re willing to pay more for stuff instead of invest that money, meaning the prices for goods rises, which affects the lower classes most. If broad income rises, the price of goods rises. Are you making more “per hour” when everything costs more and you’re still spending the same percent of your income on food and housing? And if your income goes up, and so do prices, people that didn’t get that income raise get fucked hardest. That’s basically what “runaway inflation” IS: it’s when an economy starts increasing wages to satisfy cost, and cost goes to satisfy demand, so wages go up to satisfy cost and cost goes up to satisfy demand.