Sudden market movements are destabilising even if in the medium term they are in the right direction. For this reason, there have to be concerns as well as plaudits over a 50% drop in oil prices.
Of course, lower energy prices are positive for both growth and government budgets in oil-consuming countries. A 10% fall in the oil price may translate into about a 0.1% growth increase in Europe, while countries such as India and Indonesia are using this as an opportunity to reduce the fuel subsidies that hammer their budgets.