Selling something for less than the cost of producing it. This may be used by a dominant firm to attack rivals, a strategy known to antitrust authorities as predatory pricing. Participants in international trade are often accused of dumping by domestic firms charging more than rival imports. Countries can slap duties on cheap imports that they judge are being dumped in their markets. Often this amounts to thinly disguised protectionism against more efficient foreign firms. In practice, genuine predatory pricing is rare – certainly much rarer than anti-dumping actions – because it relies on the unlikely ability of a single producer to dominate a world market. In any case, consumers gain from lower prices; so do companies that can buy their supplies more cheaply abroad.