O que vale o PIB?

John Kay, num artigo publicado no Financial Times há duas semanas que por pouco me passava despercebido:

Output seems like a hard number - and would be if it were simply a matter of counting the widgets that leave a production line. But the output of a modern economy is made up of thousands of differentiated products of changing quality and composition. The US productivity miracle was in part created, not by finding new facts about the US economy, but by reclassifying software expenditure as investment and adopting aggressive assumptions about falling computer prices.

The key number used to measure economic performance is gross domestic product. But few politicians or traders could actually define it. GDP is not, exactly, a measure of either business output or consumer welfare, although it is loosely related to both. It is safest to say that GDP is the number you arrive at if you follow an internationally agreed set of statistical conventions.

So long as everyone follows these conventions, movements in GDP tell you something about national prosperity and economic progress, even if it is not entirely clear what. But no economic data, hard or soft, can ever tell the whole story. Prosperity and progress are soft concepts and official statistics are at best a supplement, not a substitute, for evidence of eyes and ears.

Note-se, em particular, a observação sobre o milagre económico americano, assunto sobre o qual já aqui escrevi um comentário semelhante.

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