The figure that relates the speed of an object's recession in the expanding Universe to its distance in the Hubble law. It represents the current rate of expansion of the Universe. This important cosmological parameter is usually measured in units of kilometres per second per megaparsec. In the Big Bang theory, H0 varies with time and it is therefore more properly known as the Hubble parameter. In 2001 the Hubble Space Telescope Key Project team reported a final figure for H0 of 72 ± 8 km/s/Mpc. In 2010 a figure of 71 ± 2.5 km/s/Mpc was announced from the findings of the Wilkinson Microwave Anisotropy Probe.