In a 2015 report, Wayne Crews discussed the massive amount of agency regulation (dubbed "regulatory dark matter") enacted by Washington bureaucrats. Crews serves as the Vice President for Policy at the Compeitive Enterprise Insitute.
[We] lack a clear grasp on the amount and cost of the many thousands of executive branch and federal agency proclamations and issuances, including memos, guidance documents, bulletins, circulars, and announcements with practical regulatory effect. There are hundreds of “significant” agency guidance documents now in effect, plus thousands of other such documents that are subject to little scrutiny or democratic accountability.
You can read his full paper at Competitive Enterprise Institute.