In a market economy, any tendency for profit margins to continue to rise is countered largely by the entry of new competitors willing to undercut prices and by increased labor costs as more firms attempt to exploit the opportunity for outsized profits by expanding employment and output.
That increase in competitive pressure, as history has amply demonstrated, with time, returns markups to more normal levels. Over the past three decades, the share of the profits of nonfinancial corporations in the total nominal income of that sector has fluctuated around a longer-run average of roughly 10-1/2 percent.