Although better turbine design continues to improve efficiency, anticipated breakthroughs on aerodynamic design of blades have yet to materialise. Ignoring Kenetech, failures of technology are at an acceptably low level, and availability levels are still moving upwards: 98% (at least) is the norm, and 99% is common. Extrapolating from its recent installation totals in Denmark, the Danish industry reports that 287 turbines (145 MW) installed in 12 months was capacity enough to power 72,000 homes. Ten years ago, installation of 358 wind turbines amounted to 32 MW, which in 1986 met the needs of 8000 homes. The conclusion is that in ten years wind turbine generators have become five times larger, but are twice as effective, which is why energy costs have fallen tenfold.