Artwork became an important commodity in the German economy: no one in German or axis-controlled countries was allowed to invest outside of the new Germanic-controlled territory, which in turn created a self-contained market. With few options available for investments, art was of great importance to anyone with cash, including the Führer himself, as a safe form of investment, and even in trade for the lives of others. At the height of trading in 1943, art was used by Pieter de Boers, who was the head of Dutch association of Art Dealers, and the largest seller to Germans in the Netherlands, in the exchange of the release of his Jewish employee. Demand began to increase dramatically, forcing prices to rise, and only furthering the desire to discover hidden treasures within occupied territory.