English: Millions of words in the US federal tax code and regulations, 1955-2015, according to the Tax Foundation (taxfoundation.org) [1=income tax code; 2=other tax code; 3=income tax regulations; 4=other tax regulations; solid line= total, with total only for 2015]. Over this period, the US tax code and regulations grew at roughly 150,000 words per year. (A standard linear regression estimated the slope at 151,610 words per year with a standard error of 5,540 words and an adjusted coefficient of determination exceeding 99 percent.) Over this period, there have been roughly 3 words of regulations for each word in the tax code. Most of these are income tax regulations, which have recently contained 4.5 words for every word in code. The income tax code currently includes roughly 50 percent more words than other tax code, though this was reversed in 1955. For details including an adjustment to the Tax Foundation numbers incorporated here, see the UStaxWords data set in the Ecdat package for R (programming language) available from the Comprehensive R Archive Network (CRAN).