Last year the number of patent applications that were subject to a "secrecy order" (SO) under the Invention Secrecy Act of 1951 was the highest that it has been for decades, according to data obtained from the US Patent and Trademark Office and maintained on the Federation of American Scientists (FAS) site by Steven Aftergood.
Whenever disclosure of a new invention is deemed to be "detrimental to national security", a SO may be imposed on the patent application, preventing its public disclosure and blocking issuance of the patent.
As always, most affected inventions seem to involve technologies that
have military uses. FAS previously stated that the current
criteria that are used to make the determination have not been released,
so the actual scope of invention secrecy is not publicly known.
At the end of FY 2020 (September 30, 2020), there were 5,915 SOs in effect, up from 5,878 the year before.
There were 45 new orders imposed, and 8 existing orders that were rescinded. The remaining orders, which were originally imposed in previous years, were renewed. Out of the 45 new orders, 6 were Non-DoD, and all from DoE. There were also 21 "John Doe" SOs that were imposed on private inventors (i.e., not government employees or contractors). FAS claimed that "these are a constitutionally suspect category, since they involve prior restraint on the speech of a private citizen or business".
The new total of 5,915 secrecy orders in effect is higher than even 1993, when the total was 5,909.
Other useful info:
Full Disclosure of Suppressed Free Energy Patents