Since 2009, patent case filings in U.S. district courts have been rising at an alarming rate. Interestingly, there are also significant monthly fluctuations in case filings, particularly in some district courts.
The figure above shows monthly rate of new case filings since 2000. Notably, there appears to be a clear break in the trend starting around 2011, after which monthly filings increased substantially and also became more volatile. Both of these changes might be attributed to procedural changes affecting filing practices. These trends and fluctuations could adversely impact the costs and functioning of U.S. district courts.
Another issue is the location where patent litigation suits are filed. Policy makers and courts have struggled for over a quarter of a century with the “proper venue” for patent litigation. One case, TC Heartland, is currently before the Supreme Court along with a number of amicus curiae, many of which discuss behaviors such as “forum shopping” and “forum selling.”
The figure highlights the trends in filing across five major district courts: Eastern District of Texas, District of Delaware, Northern District of Illinois, Northern District of California, and Central District of California. It is notable that the Eastern District Court of Texas had over half of all of the monthly filings more than once in the past two years. The District of Delaware also had a significant share of the filings, although we observed a slight decline in its share in the last two years. One possible explanation for these changes may be that plaintiffs are increasingly targeting select district courts for their filings. It remains an open question whether forum shopping behavior explains these changes.
Figure was developed using the Patent Litigation Dataset which contains detailed patent litigation data sourced from PACER and covers the period 1963-2015. For more on these data, see the related working paper (link is external).
 While the former refers to plaintiffs selectively filing their case in a court that they perceive as being more patent-owner friendly, the latter refers to a court’s application of both procedural and substantive laws in a manner favorable to a plaintiff.