Tim Harford, the 'Undercover Economist" recently gave an oversubscribed talk at the NZ Treasury. It can be seen here.

But much shorter, and more topical and enlightening, given the pressure on US Republicans to continue letting Presidents know that legislated borrowing limits mean nothing, is Mr Harford's beautiful parable of the issues facing Congress. See Mum and Dad's attempted explanation to their 15 year old.