German investments abroad - a bad deal?

In Germany itself, critics are focusing on the fact that Germany's export surpluses are financed by lending to foreign countries, raising the question as to what the real value of our receivables actually is. Are we not getting fair value for our exports? Recent research on the matter suggests that Germany has suffered value losses on its net foreign assets corresponding to more than twenty percent of its economic output since 2006, fueled by the financial crisis.  If the analysis is indeed correct, dramatic losses on this scale raise a whole number of questions. Do the Germans have a certain penchant for speculative or purely tax-motivated investments ("dumb German money"), frittering away hard-earned current account surpluses in the process? Is it a bad idea after all for a country like Germany, subject to unfavorable demographic trends, to invest a chunk of its savings abroad on diversification grounds and given the more attractive return opportunities? Should German investors keep their money at home instead? The answer to all of these questions is "no", as a closer analysis shows.