Macro Unit 14-15 主线
Published:
[Unit 14 & 15] Money Market
（PPT 15.1）
- Money Suppliers: HH, foreign entities
- Money Demanders: Firms, Gov’t
Money Market 的图中，纵轴是 Nominal Interest Rate，横轴是 QTY of Money。
- Money Supply 是一个固定的量，因此是一条竖直的线。
- 后文的 Monetary Policy 可以 shift 它。
- Money Demand 是一条斜向下的线。
- 这是因为：Opportunity Cost of holding money is the interest you could be earning from other financial assets. Interest Rate 越高，利息就越大，OC 就越大，人们就更愿意把钱存进银行。
- Shifters:
- Price Level
- PL 上升，MD 上升。
- Income
- Tech
- US Gov’t Borrowing
- Price Level
\[MS \uparrow \implies \text{Int Rate} \downarrow \implies \text{Investment} \uparrow \implies AD \uparrow\]
[Unit 15] Loanable Funds Market
（PPT 15.1）
It shows the supply and demand of loans & the equilibrium real interest rate.
（书 P289）Loanable Funds Market 的图中，纵轴是 Real Interest Rate，横轴是 QTY of Money（也可以写 QTY of Loanable Funds，这是书上的写法）。
- The supply of loanable funds is the amount of money that is saved. (from savers / lenders)
Private Saving: the amount that households save instead of consume.
Public Saving: the amount that the government saves instead of spends.
National Savings = public + private saving- Shifters
- Changes in private savings behavior
- Changes in public savings
- Changes in foreign investment (capital inflow & outflow)
- Demand：Borrowing is the demand of loanable funds. (from borrowers / investors)
- Shifters
- Changes in borrowing by consumers
- Changes in borrowing by businesses (investment spending)
- Changes in borrowing by the government
- Gov’t Deficit Spending: Spending > Tax
- Shifters
（再次吟唱：Opportunity Cost of holding money is the interest you could be earning from other financial assets.）利率越高，OC 越高，人们就更想把钱放在银行里，而更不愿意从银行拿钱。因此 S 斜向上，D 斜向下。
e.g. 当 political instability 发生：
- demand 左移，因为 investment 下降
- supply 左移，因为外国投资者会把资本收回去，资本外逃（capital flight）。
Example (2023 MCQ #4)
Assume that the country of Alpha has a balanced budget. If the government and central bank of Alpha implement expansionary fiscal and monetary policies in order to address a recession, what effect would these policies have in the short run on the government budget and interest rates?
首先 Government Budget Deficit 不用说。
TODO:
[Unit 14] Fractional Reserve Banking
Fractional Reserve System 也叫 Limited Reserve System。
Fractional Reserve Banking
（PPT 14.1）
- Demand Deposit: Money deposited in a commercial bank in a checking account.
- Required Reserve: The percent that banks must hold by law.
- Excess Reserve: The amount that the bank can loan out or invest.
银行拿到一笔 Demand Deposit 时，会将其分为 3 个部分：
- Required Reserve：法律规定的，动不了。
- Excess Reserve：银行自己决定要拿手里的。（当然也可能不拿）
- Loanable Fund：借出去！
Money Expansion Process
借出去的部分会进入其它银行并重复这一过程。
Assume that banks keep no excess reserves, and there are no cash leakages. 每一笔钱出去之后就会进入其它银行。
模拟一下这个过程：
- 银行 A 拿到了一笔 Demand Deposit $a$ 刀。
- 银行 A 留住 $RR \times a$ 刀，借出 $(1 - RR) a$ 刀，进入银行 B。
- 创造了 $(1 - RR) a$ 刀的 money supply。
- 注：怎么创造的呢？原始存款人的账户上有 $a$ 刀，借款人获得贷款之后，账户上会有 $(1 - RR) a$ 刀，总 MS 就比原先多出来了这一部分。
- 创造了 $(1 - RR) a$ 刀的 money supply。
- 银行 B 留住 $RR (1 - RR) a$ 刀，借出 $(1-RR)^2 a$ 刀，进入银行 C。
- 创造了 $(1-RR)^2 a$ 刀的 MS。
以此类推，对于一笔凭空冒出的 Demand Deposit，总 $\Delta MS$ 的计算公式为：
\[\Delta MS = a \sum\limits_{n=0}^\infty (1 - RR)^n = \frac a {RR}\]即原先的一笔钱被放大了 $\frac 1 {RR}$ 倍：
\[\boxed{\text{Money Multiplier} = \frac 1 {\text{Reserve Requirement}}}\] \[\boxed{\Delta MS = \text{Money Multiplier} \times \text{Change in Bank Reserves}}\]Money Multiplier 也叫 Simple Multiplier。（2012 MCQ #38）
⭐[Unit 14] Ample Reserve
巴朗书上没有这一段啊
（Katie 上课）
- Commercial Banks 问美联储借钱，美联储收利息的利率叫 Discount Rate。
- Commercial Banks 在美联储存钱，收到利息的利率叫 Interest on Reserve，也叫 Administered Policy Rate。
Graph: Reserve MKT
Katie 上课画的版本是：纵轴是 Policy Rate，横轴是 Quantity of Money。（也可以写 Quantity of Reserves）
Policy Rate (也叫 Federal Funds Rate)，是商业银行之间互相借钱的利息。
- 正常情况下（当 Commercial Banks 的 Reserve 量适中，Limited Reserve），Demand 是斜向下曲线。
- 银行之间的供需关系决定 Interest Rate。准备金供给增加时，银行间借贷竞争减弱，利率下降。准备金减少时，银行更愿意支付高利率借款，利率上升。（Deepseek）
- 当利率高到一定程度时（Reserve 特别小），找其他银行借还不如找美联储，此时 Interest Rate 被 Discount Rate 完全拦住。
- 当利率高到一定程度时（Reserve 特别大，也就是 Ample Reserve），把钱放给别人还不如存在美联储拿的利息多，此时 Interest Rate 被 Interest on Reserve 完全拦住。
从 Google 上找的一个图：来源
Discount Rate 和 Interest on Reserve 是联动的，要同时上调或下降：
[Unit 14] Monetary Policy
现在出现了 Recession，你作为美联储，你要实施 Expansionary Monetary Policy（也叫 Easy Monetary Policy，增大 $MS$，以刺激经济。（反之，冷却经济的政策叫做 Contractionary Monetary Policy，也叫 Tight Monetary Policy）
美联储有四板斧：
\[\text{Expansionary} \begin{cases} \text{Limited Reserve} & \begin{cases} \text{Discount Rate} \downarrow \\ \text{Required Reserve} \downarrow \\ \text{Buy Bonds at Secondary MKT} \end{cases} \\ \text{Ample Reserve} & \begin{cases} \text{Interest on Reserve} \downarrow \\ \end{cases} \\ \end{cases}\]- Limited Reserve
- Decrease Discount Rate: 降低银行向 Fed 借钱的成本，让银行更愿意借钱，借到钱之后通过 Money Multiplier 翻倍。
- Decrease Required Reserve: 让 Money Multiplier 增加。
- Buy Bonds at Secondary Market (Open Market Operations): 买已有的 bonds，把自己的钱送出去。
- Secondary Market: the place to trade securities which have been issued at the primary MKT.
- Ample Reserve 中不用这个的原因是，给银行送钱之后，银行会存回 Fed 拿 interest on reserve 的利息。
- Ample Reserve
- Decrease Interest on Reserve: 降低银行在 Fed 这里获得的收益，让银行更愿意把钱拿去放贷。