One of the biggest was that there was an investment tax credit of 7% in the 60's and 10% in the 70's, which I believe was uncapped. I think those were also able to be rolled over to cover multiple years. That means that if you invested enough, you could pay essentially no taxes. This was repealed in 1986.
[edit] Another that I should probably mention is the treatment of asset depreciation; in the 1960's and 70's the government was incredibly generous with regards to asset depreciation. For example, they allowed more rapid depreciation so you can have assets fully depreciated while still within their useful life and potentially if you sold those would pay capital gains tax on them, meaning you reaped significant tax savings over the asset's lifetime.
That is pretty much how it is today as well. 100% bonus depreciation, Sec. 179, and the safe harbor for writing off pretty much any item under $2,500 as an expense, are all in place currently, and the favorable treatment of subsequent gain from sale is still there too.
If the subway costs $1 and 50% of the jump the turn-style 50% of the time the cost to ride the subway in aggregate is $0.75
Sure, if you take some asinine ideological hard line about the goodness or badness of taxation you'll probably get your panties in a knot but if you look at it from the perspective of who's spending money in the economy a little bit of broadly applied fraud and a little bit of tax reduction are the same thing because they shuffle money around in the same manner.
back then you could file your taxes with 6 or 7 kids and no one would check
that is not the same as claiming you have 6 or 7 kids that will be filed on your taxes and then just never filing it. Once filed he would need SSN for those kids, or he would owe taxes
