Here is a link to the 2016 report by the U.S. Office of Personnel Management if you want to look at the numbers yourself.
Official Time Usage in the
Federal Government
Fiscal Year 2016Here is the one for 2014.
Official Time Usage in the
Federal Government
Fiscal Year 2014It is done every few years and the 2018 report isn't out yet. As you can see, well over $100M dollars of taxpayer dollars each year are spent on union workers doing union business on work hours(aka taxpayer's dime) so if one wants to get mad about a union having to represent a non union member saying they are "free loading", then I will bring this up. Although I wish there was a similar report for the private sector. I am sure there would be millions of dollars there as well based on what I have seen.