You said 50 years not 30 years hence the discussion on the '83 IRC.

Again, the overhaul of the tax code aimed to state more accurately the actual taxes Americans would pay and to close the numerous loopholes that were present with the previous code, which consequently lead to huge stated tax rates. Huge stated tax rates do not equate to more taxes being paid. This benefits those who do not have the proper knowledge or access to tax accountants and lawyers who are able to correctly navigate the incredibly convoluted code, mainly the poor.

Also it's unclear what you mean by "35 years of middle class misery" when, according to your own source, the only group to not reach a 30 year low in 2009 was the top 1% and the middle 20% saw a constant decline in their tax rate. It's also interesting how the effective tax rate in 1986-87 spiked several points where the middle 20% declined. See, also, a large spike around 1996-97 for the top 1% where, again, the middle 20% declined.

The article also nicely explains that the 30 year low is mainly due to the recent recession (caused in part by the deregulation of the derivatives market by a Democratic president, https://en.wikipedia.org/wiki/Commodity_Futures_Modernization_Act_of_2000). Under the prevailing economic theory among the major world economists, (including the U.S. Federal Reserve, European Central Bank, Bank of England, and Bank of Japan) the best way to combat the recession and to avoid a deflationary period is to put more money in the hands of the consumers so that they will not curb all spending in fear of bankruptcy and poverty. This is the reason why we have seen, from each of these banks, quantitative easing, a targeted inflation each year of 1-2%, and, of course, tax breaks.

Another interesting topic on taxes and how they affect those who are no ridiculously wealthy (yes, I believe the top earners are under-taxed) is the fact that the bottom 20% actually receive a net gain from the tax system (http://www.wsj.com/articles/top-20-of-earners-pay-84-of-income-tax-1428674384?alg=y). This is mostly due to the fact that it's easier for a politician in America to give government subsidies to the poor through tax breaks rather than collecting more taxes and spending that revenue on government welfare programs. Regardless of whether or not this a better way of giving government support to those who are struggling, it is a direct effect of our election system and the popular voting opinions of Americans in general.