Must total world net exports be zero? On the Wall Street Journal Op-Ed page (Trump’s Real Trade Problem Is Money  ), John D. Mueller discusses the gold standard and claims something that I've either never heard before, don't understand, or both. 


  Many economists wrongly assume that total world net exports must equal
  zero, but in fact countries participating in the international gold
  standard had combined net exports equal to the total increase in world
  gold reserves (which in turn approximated world gold exports). As a
  result, world monetary policy was countercyclical: When the prices of
  other goods fell, the profitability of gold mining rose.


First, I thought it was tautological that global net exports had to be zero. Is Mueller's claim correct? Does it turn on a technicality of the definition of net exports? Please help me understand his position. 

Second, is it accurate to characterize gold standard monetary policy as counter-cyclical?  My understanding is that recessions in the gold standard era were marked by deflation where as in the fiat currency era recessions are merely dis-inflationary. If so, is it fair to call the gold standard substantially less counter-cyclical than fiat currency systems?
That depends on your model of the world, and on how you define "goods and services". 

In a gold standard world, you essentially exchange goods and services with gold. Gold mining is therefore simply an expansion of the money supply. Adding gold to both the nominal and real side of the economy seems to me like today adding money as a good to GDP. If you do this, you get a positive trade balance. It makes a lot of sense to seperate monetary gold, which is on the monetary side, and commodity gold, on the goods side, as Henry mentioned in the comments.

In my opinion, it does not make sense to count gold twice. It seems reasonable to seperate the monetary and real side of the world, which then would yield a balanced world trade.

To the second question: I am no expert on gold mining, but I could imagine that it is not possible to "drive up" gold production in a recession. What is true is that a (nearly) constant money/gold supply leads to inflation being counter cyclical.