Economists John Gurley and Edward Shaw pointed out that each business firm, household, or unit of government active in the financial system must conform to:R - E = FA - DWhere
R = Current income receipts
E = Expenditures out of current income
FA = Change in holdings of financial assets
D = Change in debt and equity outstanding
So, for any given time period, each economic unit must fall into one of three groups:Deficit-budget unit (DBU):
E > R, so D > FA (net borrower of funds)Surplus-budget unit (SBU):
R > E, so FA > D (net lender of funds)Balanced-budget unit (BBU):
R = E, so D = FA (neither net lender nor borrower)