"It’s true that corporations are funding a smaller share of overall government operations than they used to. In fiscal 2015, the federal government collected $343.8 billion from corporate income taxes, or 10.6% of its total revenue...Corporations also employ battalions of tax lawyers to find ways to reduce their tax bills, from running income through subsidiaries in low-tax foreign countries to moving overseas entirely, in what’s known as a corporate inversion (a practice the Treasury Department has moved to discourage)."
And if you look in the comments section you'll some good remarks about what taxes weren't included in the analysis.  I think it's fair to say that the upper 1% aren't paying nearly what they should because of the many ways they've foundcto avoid doing so.