An article in the Wall Street Journal (April 24,2013) describes a proposal to vary patent protection length by industry, rather than the US standard of 17 years. It reports the chairman of Amazon, Jeff Bezos, as suggesting 3 years as the length for the software industry, to incentivize companies to invest their money on innovation rather than patent defense. But shorter patent lengths would also reduce incentives to innovate. How should the optimal patent length be chosen for an industry ? Would differing patent lengths across industries be feasible ? How would global competitiveness of US firms be impacted by changes in the US patent length ?