The first chart below shows one view of how patent prosecution pendency is generally improving. In particular, the chart shows the percentage of patents that took more than three years from filing to issuance. As is apparent, that percentage has plummeted in President Obama’s patent office (Kappos-Rea-Lee). Unlike a few years ago, most US patents now issue within three years of filing (not counting priority claims).
The second chart tells a different story by looking at the oldest prosecution files and seeing that those have grown substantially over this same time period. In particular, the second chart shows the percentage of patents that took more than seven years to issue (filing date to issue date). For the most part, these long-pendency prosecutions involved PTAB appeals.