何謂分層隨機抽樣

目前世界各國國際組織編製綠色國民所得帳的體系主要有荷蘭統計局的 NAMEA (National Accounting Matrix including Environmental Accounts)、歐洲統計局(European System for the Collection of Economic Information on the Environment)、美國的 ENRAP (Environmental and Natural Resources Accounting Project)及聯合國的 SEEA (System of integrated Environmental and Economic Accounting)等，我國綠色國民所得帳的編主要是採用何種體系融合修訂而成？