...and what did you think was going to happen to the RPI when they cut the base rate by 1.5% at a time when the price of oil was dropping so fast? It's a weighted index that gives greater emphasis to the areas where people spend a lot of money. Of course it's going to go down and, given those two big effects, why shouldn't it go negative for a short time? All it shows is that the cost of living fell. Sustained deflation is something else.