Some environmental experts prefer physical indicators (such as "waste per capita" or "carbon dioxide emissions per year"), which may be aggregated to indices such as the "Sustainable Development Index".
有一些环保专家更喜欢物理指标（如“人均的废物值”或“每年的二氧化碳的排放量” ） ，这些可能将统计到汇总指数，如“可持续发展指数”。