The interest expense on public debt includes everything from regular debt as well as pensions and long-term liabilities, so it is very much influenced by those large numbers.
The government's debt mix, as Mr. Smith has already mentioned, is a finance issue. It is a mix of short-term and long-term borrowings. What they've done is simply updated their forecast here. I believe the reason for the decrease is the longer-term projections for interest rates are now a bit lower than was originally forecast, so that's why they've adjusted their forecasts.