Kunte et al. (1998) use their paper "Estimating National Wealth: Methodology and Results" to demonstrate that expanding the national accounts to include natural capital is a "practical necessary exercise". They estimate the total wealth of nations by including different components of wealth in their calculations, including natural capital. They place values on natural capital by using the concept of economic rent. "Economic rent is the return on a commodity in excess of the minimum required to bring forth its services. Rental value is therefore the difference between the market price and cost of production / extraction." Following this, and by adjusting calculations for (un)sustainable use patterns, they are able to determine the stock of natural capital in a country that more accurately reflects its wealth.