The production level in the same year that is registered in the "standard national income" (NI) does not meet this condition. Environmental functions and their preservation after all fall outside the NI. The NI is therefore always higher than the SNI. The difference gives information about the distance between the present production level and the production level in a sustainable situation. If the distance decreases then we are on the road to environmental sustainability, the part of the production that is based on unsustainable use of the environment decreases. If the distance increases then we are drifting further away from sustainability.