We examine how many and what kind of firms ultimately rely on foreign inputs, sell to foreign markets, and are affected by trade shocks. To capture that firms can trade indirectly by buying from or selling to domestic firms that import or export, we use Belgian data with information on both domestic firm-to-firm sales and foreign trade transactions. We find that most firms use a lot of foreign inputs, but only a small number of firms show that dependence through direct imports. While direct exporters are rare, a majority of firms are indirectly exporting. In most firms, however, indirect export is quantitatively modest, and sales at home are the key source of revenue. We show that what matters for the transmission of foreign demand shocks to a firm’s revenue is how much the firm ultimately sells to foreign markets, not whether these sales are from direct or indirect export.

We quantify the firm responses and real wage effects of foreign demand shocks. We use Belgian microdata to construct firm-specific measures of demand shocks, which capture that firms pass on foreign demand shocks to domestic suppliers. Our estimates of firm responses to these shocks suggest that firms face upward-sloping labor supply curves and have sizable fixed labor costs. We specify a general equilibrium model with these features to quantify the aggregate effects of simulated tariff shocks on wages. We find that ignoring fixed labor costs substantially underestimates aggregate effects on wages, whereas incorporating upward-sloping labor supply appears less consequential.