This week's quiz question:

The volume of global trade decreased how much in 2009?

a) 3 percent    b) 12 percent    c) 23 percent

Answer after the jump …

B, 12 percent. In the biggest decline since World War II, the volume of global trade contracted 12.2 percent, according to the World Trade Organization (WTO), with the primary cause being a huge drop in global demand. Since 1965, trade volume has fallen only three other times: 1975 (-7 percent), 1982 (-2 percent), and 2001 (-0.2 percent) -- see the graph below. In terms of dollar value, world merchandise trade fell 23 percent, mostly due to falls in the prices of oil and other commodities. Generally, though, volume is better for year-to-year comparisons because volume isn't distorted by currency and commodity-price fluctuations.

The good news, according to the WTO: This year exports are estimated to grow 9.5 percent in terms of volume. That's not enough to cancel out last year's plunge, but if the growth continued in 2011, then trade volume would surpass its 2008 peak.