What can't speak can't lie

I have ground the figures from here to produce the following three charts for the twelve countries now in the Euro-zone. The x-axis is "government debt-to-GDP ratio" and the y-axis is "average interest rate paid on government borrowing", and the charts are for 1996, 2000 and 2008 respectively. You can click to enlarge but then they are too big for the screen.
I accept that correlation is not causation; that there is a wide variation around the trendline (which is Excel-generated), and that in proper science it is difficult to 'prove' anything [etc etc], but to me, these charts strongly suggest that the level of government borrowing relative to GDP has a major impact on the interest rate that the government has to pay.

Other major factors would be the average period to maturity of government debt (at the time it was issued) because longer-dated bonds tend to pay a higher interest rate than shorter dated ones (and the UK government is currently only paying 0.5% interest on £150 billion of its debts, i.e. on sight deposits made by commercial banks at the Bank of England which arose from the whole QE shenanigans). And I also accept that the underlying figures may be wrong - but at least they are consistently wrong, and so on [etc etc].

But I don't think much of the alternative explanation given by Richard Werner who works for this fund manager in the comments to my post of last Friday: "the interest rate is a function of (and perhaps mainly determined by) the success of the relevant national debt agency (or Ministry of Finance) in timing and apportioning tranches of bond issues."

Anyways, make up your own minds on this one.