Answer based on context:

While reliable figures are difficult to obtain, estimated global sales of The Hobbit run between 35 and 100 million copies since 1937. In the UK The Hobbit has not retreated from the top 5,000 books of Nielsen BookScan since 1995, when the index began, achieving a three-year sales peak rising from 33,084 (2000) to 142,541 (2001), 126,771 (2002) and 61,229 (2003), ranking it at the 3rd position in Nielsens "Evergreen" book list. The enduring popularity of The Hobbit makes early printings of the book attractive collectors items. The first printing of the first English-language edition can sell for between £6,000 and £20,000 at auction, although the price for a signed first edition has reached over £60,000.

How many more copies of the Hobbit sold in 2002 and 2003 than 2000 and 2001?
12375