货币扩张

货币扩张，也称作货币创造(Money creation)，是中央银行、商业银行和非银行（机构或个人）透过信贷关系共同作用，使得在银行体系内流通货币量扩大的金融行为。
对货币扩张的控制是中央银行的主要任务之一。
不是所有的流通货币都需要有货币现金、实物资产或政府资产作后盾。一国的货币是以国家的经济潜力或政府的法定货币法令作后盾的。这种潜力也成为政府发行货币的理论上限。

**货币扩张乘数**
货币扩张乘数，也称作存款创造乘数，描述商业银行体系供给货币的机制，它衡量了商业银行体系内增加货币供给的数量。为了控制这个体系创造的货币量，中央银行给商业银行设置严格的准备金比例，中央银行只允许商业银行的初级存款的一部分用于放贷，这也称作现金准备比例。

**货币扩张乘数示例**
某储户在银行A存入1000元初级存款(银行负债部分的存款)，现金准备比例为12%，则120元必须被银行保留(银行资产部分的储备)，880元可用于放贷(银行资产部分的贷款)。如果银行A将超额储备880元全部放贷，接受贷款的人将之存到银行B，银行B需要将12%×880元作为初级存款880元的现金储备，可放贷部分为774.40元。如果774.40元被存入C银行，则92.93元须作为储备，可以放贷681.47元，……，以此类推，直至不再有超额储备(此处为了简化，忽略了安全储备)。
*TD：总存款的变化量
*ID：存款的初始变化
*crr：现金准备比例
例如，如果准备金比例为12%，存款的初始增长1000元将使总存款增加8333.33元(1000/.12=8333.33)。

**美元货币扩张示例**
#美国政府发行国库券，即在特定日期支付特定金额的支付承诺。比如发行价值1,000,000美元的债券，投资者以货币进行投资购入债券，以获得债券利息为报偿。
#美联储印刷价值1,000,000美元的支票，作为应付款项给美国政府。该支票就是销售债券的进款。
#

**模型构建**
B：实际资本 D：总资本 C：现金提取量 rd：活期存款准备金率 rt：定期存款准备金率 k：现金漏出率=C/D

**模型构建第一步**
B=rd×D+C
D=B/(rd+k）

**模型构建第二步**
引入超额准备金 Re e：超额准备金率
B=rd×D+C+Re
D=B/(rd+e+k）

**模型构建第三步**
引入定期存款T (t,定期存款占活期存款比例）
B=rdXD+rt×T+C+Re
D=B/(rd+rt×t+e+k）

**延伸阅读**
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