The ACCC estimates that in 2016-17, Queenslanders will be paying the most for their electricity, followed by South Australians and people living in New South Wales. Victorians will have the lowest electricity bills. On average across the NEM, a 2015-16 residential bill was $1,524 (excluding GST), made up of network costs (48%), wholesale costs (22%), environmental costs (7%), retail and other costs (16%) and retail margins (8%). The ACCC attributed the main reason for electricity price increases to higher network costs for all states other than South Australia, where generation costs represented the highest increase. "The wholesale (generation) market is highly concentrated and this is likely to be contributing to higher wholesale electricity prices." The ACCC accused the network operators of "over-investing" in poles and wires and gaming rules around revenue. The ‘big three’ vertically integrated gentailers, AGL, Origin, and EnergyAustralia, continue to hold large retail market shares in most regions, and control in excess of 60% of generation capacity in NSW, South Australia, and Victoria making it difficult for smaller retailers to compete. Retail margins increased significantly in NSW, but decreased in others.