程阳：国际货币基金组织的预测很靠谱

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How accurate are the IMF's forecasts?

ON JULY 16th the IMF released its new forecasts for the world economy. It currently expects global growth of 3.5% in 2012 and 3.9% in 2013. How accurate are these forecasts and how much attention should we pay to them? The Economist has dug out historical IMF forecasts made as far back as April 1999 and compared them to the actual figures. On average, over the 12 years for which data exist, the IMF underestimated growth by 0.3 percentage points in the immediate forecast year, but overestimated growth in the following forecast year by 0.2 percentage points (the average absolute error is much larger at 0.6 and 1.4 percentage points respectively). The Fund does gauge general sentiment well; it correctly anticipated the change in pace of GDP growth (ie, whether GDP was increasing at a slower or faster rate) for 18 of the 24 forecasts (between 1999 and 2011). What does this tell us about the forthcoming years? In their latest forecasts, the IMF emphasises that much depends on outcomes in America and Europe. So barring a big shock to the world economy (a Greek exit from the euro area for example), expect the Fund's forecasts today to stand up fairly well.

7月16日，国际货币基金组织发布了对全球经济的最新预测。当前它对2012年和2013年全球经济增长率的预测为3.5%和3.9%。这些预测有多准确？我们应该在多大程度上重视这些预测？《经济学人》挖掘出国际货币基金组织历史上作出的预测（从1999年4月开始统计），并将这些预测与实际数字进行比较。平均起来，在有据可查的12年间，国际货币基金组织低估了下一年份0.3个百分点，而又高估了下一年份随后一年0.2个百分点（平均绝对误差大得多，分别为0.6%和1.4%）。国际货币基金组织在判断整体情绪方面做得不错。在1999年至2011年对GDP增长速率变化（即GDP会以较慢或是较快速率增长）的24次预测中，国际货币基金组织对了18次。这对于未来一年有何启示？国际货币基金组织在最新预测中强调美国和欧洲的出口会决定许多问题。所以，如果全球经济没有遭受巨大冲击（比如希腊从欧元区退出），估计国际货币基金组织当前的预测能够很好地站住脚。