The spread when the graph starts is about 50 basis points. When the graph ends about 130 basis points. So the increase is about 160% over that period to time which is due to the financial crisis which started in 2007. So they have a long way to go to get back to normal.
Now perhaps Swan is being disingenuous by mentioning 2008 as the start of teh financial crisis as by then spreads had already doubled to about 100 basis points. As for your comment that the guaranteed debt costs more, this is technically correct- it look like about 2 basis point out of 130 basis point on the graph, but effectively they cost about the same. This is why the majors have continued to use the guarantee - whilst a few basis more expensive, it provided them with an alternative source of funding and thus clears headroom for investors in the banks non-guaranteed debt.
