Patent Troll Index: who sues, who gets sued, and how it ends
How many US patent lawsuits patent trolls file each year, how many companies they sue, and how quickly those suits end, counted from the federal court record.
Federal court cases filed through December 31, 2025. Updated September 25, 2026.
What we mean by patent troll. This index uses “patent troll” because it is the common term. The legal terms are non-practicing entity and patent assertion entity: a business that holds patents in order to sue over them, and makes nothing. The index counts that activity across the federal court record and does not name any company.
Imagine you build a small software company. One day a letter arrives.
It says your product infringes a patent and asks you to pay, or face a lawsuit.
You have never heard of the company that sent it. It sells no product. What it has is a patent bought from someone else, and a lawyer.
You have two choices.
Dear ,
We represent the owner of U.S. Patent No. . We have reviewed your product and believe it infringes one or more claims of that patent.
We are prepared to offer a license on reasonable terms. If we do not hear from you within thirty days, our client intends to file suit.
Sincerely,
Fight in court
- Lawyers and discovery
- Often several years
- A ruling only if the case gets that far
Pay them to go away
- A payment
- Settled within months
- Usually cheaper, even with a strong defense
What most companies choose
Paying is usually much cheaper than fighting, even for a company that did nothing wrong and would likely beat a weak patent in court.
So most companies pay. The price tends to track what a defense would have cost, not what the invention is worth.
The Federal Trade Commission reached the same conclusion in its 2016 study of patent assertion entities: most of their settlements cost less than defending the case would have.
The result works like a tax on making products, one that no legislature set and no budget records. This index measures it every year.
Step 1
How many patent suits are filed each year
Every US patent lawsuit is filed in a federal court, and the clerks record each one in a public database that anyone can download. Here is how many were filed each year, before any judgment about who filed them.
Patent lawsuits filed in US federal courts, 2000 to 2025
89,639suits in all
In 2000 the federal district courts took 2,222 patent suits. The count peaked at 5,829 in 2013, 2.6× as many, and was 4,277 in 2025, the latest full year. That is 89,639 suits in all. Source: the Federal Judicial Center's public record of civil cases.
Step 2
Which of them come from patent trolls
Most of those lawsuits are ordinary disputes: a company that built something sues a company it believes copied it.
This index looks for the rest, brought by companies that sue over patents but do not make products.
No government publishes a list of those companies. Commercial lists exist, but they are paid products and do not say how they were built, so their results cannot be checked or repeated.
We built our own from public records.
Step 3
The four public sources
The index uses four public sources. Each file is downloaded and kept exactly as it was published.
Who sued whom, when, and how it ended
Federal Judicial Center
Who bought a patent from someone else
US Patent and Trademark Office
Which companies report to the stock-market regulator
Securities and Exchange Commission
Party names and case events from court dockets
CourtListener (non-profit)
Step 4
Four questions about each plaintiff
Every company that files a patent lawsuit is checked against four questions. No single answer decides it. A company is counted when its answers, taken together, fit the definition above.
37,054 companies have filed a patent lawsuit in these years, which makes 60,559 plaintiff-years (one company suing in one year). 6,648 of those plaintiff-years meet the definition.
- 1
Did they buy the patent from someone else?
A company that invented something usually keeps it. Buying a patent you had no part in making is the first sign.
- 2
Do they sue over and over?
A single suit is usually an ordinary dispute. Suing many companies, again and again, is typical of the businesses counted here.
- 3
Does anyone ever sue them, and do they report to the stock-market regulator?
Companies that make products get sued too, and many file public reports with the SEC. A company that does neither is unlikely to be selling anything.
- 4
Are they a medicine company?
Drug makers sue each other under a separate legal process for generic medicines, explained below. Those suits are left out.
Why medicine companies are taken out
Drug patents are litigated under their own rules. Under the Hatch-Waxman Act, a company that applies to sell a generic version of a patented medicine, and tells the FDA the patent is invalid or would not be infringed, is treated by law as having infringed it at that point. The maker of the original drug usually sues within 45 days, before the generic reaches pharmacies.
These suits are between two companies that both make medicines, and they follow most such challenges. A drug maker can be in court dozens of times a year without buying a patent from anyone. Counting those suits would treat routine generic-drug cases as repeat suing and raise the share for reasons unrelated to patent trolls.
Step 5
How the results compare with academic research
Two university research teams have each published their own classification of patent plaintiffs. We compared our results with both, on the same 1,081 companies.
We also compared the two teams with each other, to show how often experts disagree when they classify the same companies.
RTI compared with the first team
RTI × researchers
9.51%
of suits classified differently
The two research teams compared
Researchers × researchers
9.17%
of suits classified differently
0.34pp
Percentage points: how much more often we differ from the first team than the two teams differ from each other.
The same check, counted per company
The same comparison with the first team, counting each company once rather than once per suit. It covers every company that team classified, which is why it includes more companies than the comparison above.
Agreement · counted per company
When we flag a company, do the researchers agree?
79.8%
likely range: 77.1% to 82.3%
confirmed by the researchers727
classified differently184
Coverage · counted per company
How many of the researchers’ trolls do we find?
60.4%
likely range: 57.6% to 63.2%
found727
not found476
We compared 4,772 companies. We and the researchers agree that 3,385 of them are not patent trolls. Another 1,797 companies on the researchers' list are outside the lawsuits this index covers.
Step 6
What the count shows
Here is the chart from the first step again, with the suits filed by patent trolls in red.
Patent lawsuits filed in US federal courts, 2000 to 2025, by who filed them
In 2000 to 2004, patent trolls filed 9.2% of US patent suits. In 2010 the share rose 1.9×, the largest one-year increase on record. It passed half of all suits in 2012. It peaked at 62.1% in 2015, 6.8× the 2000 to 2004 level.
Through the 2000s the share stayed between 6.7% and 15.2%. It rose in 2010, peaked in 2015, and since 2016 it has stayed between 48.0% and 59.4%.
The comparisons on the rest of this page use those three periods: before 2010, 2010 to 2015, and after 2015.
The lowest share after 2015 (48.0%, in 2018) was 3.2× the highest share before 2010 (15.2%, in 2009).
2000 to 2009
10.9%
average share of US patent suits filed by patent trolls
2016 to 2025
53.0%
average share since then
What changed for the companies being sued
How many companies were sued
Patent trolls sued 1,615 companies in 2025, against an average of 210 a year in 2000 to 2004. The peak was 2,497 companies in 2015.
The squares count company-years: one company sued in one year. A company sued in three different years counts three times. Gray squares are the years before 2010, red squares 2010 onward. Across 2000 to 2025 that adds up to 26,870 company-years.
One square = 250 company-years
Before 2010
2,446
company-years · 10 years
2010 to 2015
10,317
company-years · 6 years
After 2015
14,107
company-years · 10 years
More of these suits end before any ruling
Settlement amounts are not published, but the court record shows when each case ended. Of the 1,590 troll suits that ended in 2025, 866 (54.5%) were dropped or settled within six months of filing, against 24.9% in 2000 to 2004.
When the two sides drop or settle a case that quickly, it ends before any court has ruled on whether the patent was infringed.
- Before 201023.9%
644 of 2,692 suits that ended · bar length shows how many ended in the period
- 2010 to 201527.0%
3,896 of 14,407 suits that ended · bar length shows how many ended in the period
- After 201544.5%
8,191 of 18,425 suits that ended · bar length shows how many ended in the period
Source: Federal Judicial Center, Integrated Database of civil cases in the federal district courts.
Patent trolls, in short
Based on the 89,639 patent lawsuits in this index.
What is a patent troll?
A company that makes its money by suing over patents, usually ones it bought, rather than by selling products. The legal terms are patent assertion entity and non-practicing entity.
How many US patent lawsuits do patent trolls file?
In 2025, 52.2% of US patent suits were filed by patent trolls, up from 9.2% in 2000 to 2004.
How many companies get sued by patent trolls each year?
Patent trolls sued 1,615 companies in 2025. The peak was 2,497 in 2015.
How do patent troll lawsuits usually end?
Most are dropped or settled early. Of the troll suits that ended in 2025, 54.5% were dropped or settled within six months of filing, before any ruling on whether the patent was infringed.
Where does the data come from?
From the Federal Judicial Center's Integrated Database, the federal courts' public record of civil cases: 89,639 patent suits filed from 2000 to 2025. Patent ownership comes from the USPTO and company filings from the SEC.
Sources: Federal Judicial Center Integrated Database, civil cases; USPTO Assignment Center; SEC EDGAR company list; CourtListener RECAP.
Last refreshed September 25, 2026