According to Fortune Magazine, the top five (revenue) private firms accounted or something like $343 billion in sales. This group includes Koch Industries, Cargill, Chrysler, Kaiser Permanente and the US Postal Service, which is technically not part of the US Government.
It’s interesting to note that of these firms, the Postal Service accounted for 21% of the revenue generated, but required 62% of the 1.253 million employees to generate that combined pool of $343B in revenue. Looking at it that way, maybe a 1 cent increase in postage isn’t all that bad after all!