打个比方,薯老打算改行开银行了,自己出资$50刀买了个小电话亭做银行生意,柠檬表示支持,卖了手里的财政部$100债券给Fed, Fed印了$100给柠檬,转手这$100就存到田薯银行。田薯银行的会计报表(balance sheet)说:
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Asset:
Phone Booth: $50
Cash: $100 (存在Fed)
Total Asset = $150
--------------------------------------------------------
Liability:
Checking Account: $100 (柠檬存的的钱)
--------------------------------------------------------
Equity: $50 (薯老自己投资)
=============================================================================
这$100 都放在Fed每天挣点小钱
Required Reserve 只是柠檬存钱的10%,$10,所以田薯银行有$90 Excess Reserve,符合监管没问题。
按Dodd-Frank, Tier 1 Asset Ratio = $50/$150 = 33%,超过要求很多,没问题。
假定田薯银行把这$90 Excess Reserve写张支票全借给快牛,而快牛借到的钱暂时又都存回田薯银行(大家都是一个坛子的,都支持薯老开银行),那么新的会计报表是:
=============================================================================
Asset:
Phone Booth $50
Cash $100 (还是存在Fed)
Loan $90
Total Asset = $240
---------------------------------------------------
Liability:
Checking Account: $190 = $100 (原存户)+ $90 (新存户)
---------------------------------
Equity:
$50
=============================================================================
现在checking account 柠檬+快牛存的钱是$190,比原来多了$90,注意这个$90是田薯银行印的,不是Fed印的。储备金要求是$19,所以田薯银行还有$81能出借,符合监管没问题…
一直这么借、存滚下去,田薯银行收到柠檬的$100,可以借出(印出)$100 * (0.9 + 0.9*0.9 + 0.9*0.9*0.9 …. ) = $900 (Fed印的$100变成了市面流通的$1,000 = $100 / 10%)。
最后会计报表:
=============================================================================
Asset:
Phone Booth $50
Cash $100 (还是存在Fed)
Loan $900
Total Asset = $1,050
---------------------------------------------------
Liability:
Checking Account: $1,000
---------------------------------
Equity:
$50
=============================================================================
存款是$1,000,required reserve 是 10%, $100,刚好不多不少,满足fractional banking 监管,也没有多余的钱可出借了。
可是按Dodd-Frank,Tier 1 Asset Ratio = $50 (phone booth) / $1,050 = 4.8%,有点玄。大概田薯银行不能全额出借$900。
要不再投$50买第二个电话亭?反正大家都用手机,电话亭闲着也是闲着,开个田薯银行第二分行比较经济实惠。
薯老还可以忽悠柠檬买田薯银行股份。如果柠檬把存的$100都去买了田薯银行股份,那么Liability就变成$900,Equity变成$150,Asset没变。Dodd-Frank,Tier 1 Asset Ratio = $150 / $1,050 = 14.3%,没问题了
因为存款现在是$900,required reserve 是10%,$90,那个100存在Fed又多了$10 Excess Reserve,类推下去,还能继续贷$100款出去,这样Asset 与 Libility 都增加$100,Asset = $1,150, Liability = $1,000,正好满足fractional banking 监管。Dodd-Frank,Tier 1 Asset Ratio = $150 / $1,150 = 13.0%,还是没问题
【再加一小段】
如果柠檬没把$100银行债务转成银行股份,那么Asset里面的loan只要坏掉$50以上,银行就破产了(资不抵债)。柠檬转了$100银行债务到银行股份,那么loan要坏掉$150以上银行才会破产。Dodd-Frank降低了商业银行破产的概率,也提高了商业银行破产时自己损失的份额(more meat in the game, so be more careful when making loan)
Fractional banking说收100刀存款只允许贷出90刀。Dodd-Frank 说股东没有肉在银行里,收了存款也不许贷出。