Cost-weighted aggregate markup \(\mathcal{M}\) computed from the firm-level markups \(\mu_{it}(s)\) constructed using micro data from the US Census of Manufactures from \(1972\) to \(2012\), as discussed in the text, for different values of the returns to scale (RTS). Our benchmark model assumes constant returns to scale, RTS \(=1\), but our results are robust to lower returns to scale.