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>>> To keep them valid, companies must pay maintenance fees every four years. I wonder how many patents are invalid because of neglect.

• DougBTX 16y ago
  The fees are higher than I expected: http://www.the-business-of-patents.com/patent-maintenance-fees.html http://www.the-business-of-patents.com/patent-maintenance-fe...
• kljensen 16y ago
  About 1,000 per week miss their fees. (In contrast 2k+ are granted each week.)