20190404 PB=（ROE-g）/(COE-g)

另一個著名的股票估值方程式是：
PB=（ROE-g）/(COE-g)

或 Target P / BV = ( ROE – g ) / ( CoE – g ) 
Target P = BV*( ROE – g ) / ( CoE – g ) 

where P = Share Price 
BV = Book Value per Share 
ROE = Return on Equity 
CoE = Cost of (Equity) Capital 
g = Long Term Growth Rate 
P0 = D1 / (r − g)
P0/E1 = (D1 /E1) / (r − g)
P0/E1 = (1 − b) / (r − g)
P0 / (B0 × ROE) = (1 − b) / (r − g)
P0/B0 = [ROE × (1 − b)] / (r − g)
P0/B0 = [ROE – (ROE × b)] / (r − g)
P0/B0 = (ROE – g) / (r − g)
r=COE=rf+(rm-rf)*beta 
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例：恆生銀行(0011)
P0=198.4  D0=7.5  DG=7.58%
BV=84.778  
ROE=15.2% (五年平均)
COE=11.68%         
COE=(D0(1+DG)/P0)+DG=7.5*1.0758/198.4+0.0758=11.65
g=8.02 (EPS growth 五年平均)
∴目標價 P=84.778*(15.2-8.02)/(11.68-8.02) = 164.44
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另一個消除g的估值方程式是：

Target P = BV*PB/exp( ROE – CoE) 

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例：恆生銀行(0011)
BV=84.778  
ROE=15.2 (五年平均)
COE=11.68
PB=2.47
∴目標價 P=84.778*2.47/exp((15.2-11.68)/100) = 202.32