The principal market data, maximum, minimum and yearly average prices, hourly volatility as well as hours with negative prices are reported in Table 3.4. The period analysed has been characterised by a large variability in electricity prices, driven by large changes in the raw material prices, the introduction in Europe of a carbon pricing mechanism and by large variations in the demand curve due to the economical crisis of 2008-2009. As expected, hourly intraday prices show even higher volatility, with prices that exceeded EUR 1000/MWh and negative prices as low as EUR -500/MWh.