In the case of patentable ideas such as the wheelbarrow, the idea of unpriced spillovers is more plausible. Yet there is no reason to believe that it is of practical importance. Indeed, there is a modern example of the wheelbarrow – that of Travelpro – the inventor of the modern wheeled roll-on suitcase with a retractable handle. Obviously such an idea can not both be useful and be secret – and once you see a wheeled roll-on suitcase it is not difficult to figure out how to make one of your own. Needless to say, Travelpro was quickly imitated – and so quickly you probably have never even heard of Travelpro. Never-the-less – despite their inability to garner an intellectual monopoly over their invention – they found it worthwhile to innovate – and they still do a lucrative business today, claiming “425,000 Flight Crew Members Worldwide Choose Travelpro Luggage.