How many patents have terminal disclaimers (i.e., truncation in their time to expiry)? I am looking for a percentage of the total population of patents granted. A rough estimate + source is good enough.
Is there an easy way to tell if a specific patent have been terminally disclaimed?
The USPTO put out a working paper in June 2015 titled "The USPTO Historical Patent Data Files: Two centuries of invention". In it they state "Internal estimates suggest that 11.9% of patents granted in 2012 contain terminal disclaimers. This rate has increased
from 3.4% in 1990; thus we expect this to become an increasing problem with respect to calculating the expiration date of
patents in the future." See footnote 36, page 12.
You can also go to http://patft.uspto.gov/ and insert patent number in the full-page image. You retrive the patent specification as published and if there is a terminal disclaimer you will find it printed clearly on the first page, left column.
No source for statistics but I am guessing the more patents there are in the same family, the more likely it will be that they will be terminally disclaimed.