According to art experts in Europe, as of 2013 there are still roughly 100,000 artworks that were stolen by the Nazis that are still missing. The value of the artwork based on modern-day valuations is $10 Billion.
Source: Patricia Cohen and Tom Mashberg, “Family, ‘Not Willing to Forget,’ Pursues Art It Lost to Nazis,” New York Times, April 26,2013.