According to a recent Forbes.com article (link below) referencing the World Intellectual Property Organization (WIPO) Patent Report released on Monday, 2004 statistics show that while Japan and the United States still lead the world in total patent application filings, China is quickly moving up the list. In 2004, 423,081 patent applications were filed in Japan, compared to 356,943 in the United States. The Republic of Korea was third with 140,115, China fourth with 130,384, and 155,000 patent applications were filed with the European Patent Office (noting that this is the only non-country on the list). The next countries, in decreasing order of patent applications filed, are Germany, Canada, Australia, the Russian Federation, the United Kingdom, Brazil, India, France, Mexico, and Norway. Additional data is also provided showing the number of patent filings per billion U.S. dollars in gross domestic product (GDP), as well as the number of patent filings per million people in the country. One surprising change of note was the increase in patent applications filed in China between 2000 and 2004, which nearly doubled during that time period. I note that the article does not appear to take into consideration the fact that a significant portion of these applications are filed internationally, but the actual WIPO data shows a distinction between "resident" applications and "non-resident" applications (see link to graph below).

Forbes.com Article: LINK
WIPO Patent Report: Statistics on Worldwide Patent Activity (2006 Edition): LINK
Top 20 Patent Offices for Filing Applications (Chart): LINK