The point that mattes is not that 90 countries use PR.
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What matters is that all of the most successful countries now use PR.  Since the end of WWII, the leading countries that use PR have steadily overtaken the leading countries that use FPTP.
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It turns out that the true generators of economic prosperity are our democratic institutions, and the stronger and more democratic the institutions of government, the stronger the economy. 
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In terms of economic performance and economic competitiveness, FPTP is simply inferior to PR.