Cyrusb,
Perhaps 3600 is generous, however, I live in the middle of nowhere, 350 miles to a oil lamp dealer, and I have seen 7 oil lamps in a town of 20,000 people. That pencils out to 1 lamp per 2,857 people.
Assuming there are approximately 400,000,000 people in USA, that would mean there are 140,007 oil lamps imported into USA (hmm.........that seems excessive) I will stick to 3600 lamp estimate.
I am still looking for the Dept or Commerce data to get more accurate figures. If I find that data, I will post it.