National accounting has focused on man-made capital. Capital consumption, or depreciation, has been subtracted from gross domestic product, giving a net domestic product figure which is sustainable in the sense that one can consume that amount while maintaining the capital stock intact. This concept does not take into account consumption of the "natural" or environmental capital. It is possible to estimate environmentally adjusted net domestic product by subtracting environmental depletion and degradation allowances from the standard net domestic product figures.