Over 30% of USPTO revenue is derived from maintenance fees that are paid by patent holders. Under the current fee structure, three post-grant maintenance fees must be paid in order to keep a patent from prematurely expiring. A large entity pays $980 3.5 years after issuance; $2,480 7.5 years after issuance; and $4,110 11.5 after issuance. If the fee is not paid then the patent will expire at the next 4, 8, or 12 year mark. This is easy-money for the USPTO because because it does not involve any agency operational budget other than the expense of actually collecting the fee.
I used the USPTO’s new maintenance-fee data to create the charts below that show historic maintenance fee payments. The first chart might be designated a “survival rate” chart. In particular, the chart shows the percent of patents whose maintenance fees were paid at each of the the four (blue), eight (red), and twelve (green) year marks.
The graph generally shows that the rate of patent maintenance fee payments has been declining for about the past year-and-a-half.
Of the 100,000+ patents issued in 1997, fewer than 50% are still in-force.