In 2001 Hall, Jaffe, and Trajtenberg published “The NBER Patent Citation Data File: Lessons, Insights and Methodological Tools.” NBER Working Paper 8498. They condensed 418 USPTO patent classifications down to six super classifications and made their data available to the public (with the caveat, in all caps, that people using their data site their work as I dutifully just did).
Their concept was so well received that even the patent office played along! I found a csv file on uspto.gov with counts of patents in each NBER sub category for the years 1840-2014. Not to be out done, the patent office published The USPTO Historical Patent Data Files: Two centuries of innovation, made their data available, and requested that users site their work (though the request was not in all caps).
As fun a reading published works is, it’s way more fun to load their data into a database to see what interesting things it can be made to do. Here’s a mapping of the NBER categories and sub categories to their uspto classes. If you pick a category or sub category you can drill down to get the patent counts provided by the uspto. I also created the reverse list (uspto class to nber category and sub category). How fun is that?