Statistics from the OECD
The OECD (the Organisation for Economic Co-operation and Development) has a great deal of statistics and reports available.
If you want a reference their statistics and reports are a good reference. You can use their material, but not for commercial purposes, and you need to give appropriate copyright credits. More on how you do that here:
In fact the OECD encourages you to use their material in presentations, teaching materials etc.
The starting point to explore this could be their library under this link:
We are adding a few international overviews from their materials. All are of course ©OECD. The one of gross national debt vs net debt is from their Jan 2014 newsletter. The others from their statistical data base + from their publication on VAT and Consumption taxes.
See these as examples for your own exploration. Other statistics of interest may for instance be spending on health care or on pharmaceuticals.
OECD statistics on total tax revenues vs GNP, updated Oct 14th 2014