The Surest Measure of How China's Losing

American presidential elections are a patchy time for the use of facts. It turns out presidential transitions are, too. Donald Trump as president-elect has triggered a slew of comments and articles about China’s pending leadership of the world economy. Journalists and pundits may value words over money; economists should not. There are data, grounded in real-world calculations, that show China’s economic importance falling -- not rising slowly, nor staying stable, but falling.