A government that can issue debt in its own currency can easily keep interest rates low. The rates are bounded by concerns about inflation, over-expansion of the state sector, and the central bank's independence; but, with our relatively low levels of debt (Japan's debt amounts to over 230% of its GDP) and depressed output and inflation, these limits are quite distant in the UK and the US. And as the record bears out, continuous increases in both countries' national debt since the crash have been accompanied by a fall in the cost of government borrowing to near zero.