I would say that because of posters and and radio ad's, people were sent into a sense that if they didn't help out in some way, people might think less of them, so they spent the spare money they had on donations, items and other things that were put into Americas economy.
Also, throughout the war, all items that were of any value were kept by the soldiers and brought back into America when the war was over or due to the large amounts of silverware found in the raided rich parts of Germany would have fetched a good price.
