The Singapore electricity industry had traditionally been vertically integrated and Government-owned. Tremendous progress has been made since 1995 to liberalise the electricity industry for greater efficiency and innovation. The electricity generation and retail business was separated from the natural monopoly of electricity transmission at the ownership level in 2001. The National Electricity Market of Singapore (NEMS) commenced operation on 1 Jan 2003. In the NEMS, which is essentially a real-time electricity trading pool, generation companies compete to sell electricity every half-hour. In addition to electricity, trading of operating reserves to maintain system security and reliability also takes place in the NEMS on a half-hourly basis. Electricity retailers buy electricity from the NEMS and offer packages to sell electricity to contestable consumers.