How Dumb is Donald Trump?

In his campaign kick-off, Donald Trump said a bunch of stupid things. His comments about Mexican illegal immigrants got the most attention, but he also said:

“When did we beat Japan at anything?”

When' just a couple days later, the USA beat Japan in the Women's World Cup (USA! USA!) a lot of people took pleasure in laughing at The Donald. :

Even before the game though, it was a really, really stupid thing to say (even by Trump’s standards). Is he not aware of what has been called Japan’s ‘Lost Decade’? Is he stuck in the ’90s or something?

The Lost Decade ... is the time after the Japanese asset price bubble's collapse within the Japanese economy. The term originally referred to the years from 1991 to 2000, but recently the decade from 2001 to 2010 is often included, so that the whole period of the 1990s to the present is referred to as the Lost Two Decades or the Lost 20 Years... Over the period of 1995 to 2007, GDP fell from $5.33 to $4.36 trillion in nominal terms, real wages fell around 5%, while the country experienced a stagnant price level. While there is some debate on the extent and measurement of Japan's setbacks, the economic effect of the Lost Decade is well established and Japanese policymakers continue to grapple with its consequences.

What Trump said was the sort of thing people were saying twenty-five years ago.