Two developments relevant to the national accounts since the 1980s include the following. Generational accounting is a method for measuring redistribution of lifetime tax burdens across generations from social insurance, including social security and social health insurance. It has been proposed as a better guide to the sustainability of a fiscal policy than budget deficits, which reflect only taxes minus spending in the current year.   • Jagadeesh Gokhale, 2008. "generational accounting." "The New Palgrave Dictionary of Economics", 2nd Edition. Abstract and uncorrected proof.   • Laurence J. Kotlikoff, 1992. "Generational Accounting: Knowing Who Pays, and When, for What We Spend". Free Press. Review extract.</ref> Environmental or green national accounting is the method of valuing environmental assets, which are usually not counted in measuring national wealth, in part due to the difficulty of valuing them. The method has been proposed as an alternative to an implied zero valuation of environmental assets and as a way of measuring the sustainability of welfare levels in the presence of environmental degradation.   • "green national accounting" by Sjak Smulders   • "sustainability' by Daniel W. Bromley   • National Research Council, 1994. "Assigning Economic Value to Natural Resources", National Academy Press. Chapter links.</ref>