不明白呢！！！！！！！！

growth rate g = retention rate b * Return on Equity ROE

image as followings:
year 1: your net income is NI, the portion that is not distributed is:  NI * b; this is the total amount to be invested at the end of year 1
next year: you invested the kept portion of NI*b, the return on it is NI*b*ROE, again you are going to kept some portion, NI*b*ROE*b, which will not be distributed. Considering the amount you already have had in year 1, now totally you have NI*b + NI*b*ROE*b, at the end of year 2 that can be invested in the following year

Thus, the growth rate g is: [(NI*b+NI*b*ROE*b) - NI*b] / NI*b =  b*ROE

说得好！

好的  学习了谢谢

思路很好，但是好像有点不对。第一年的股利是D0=NI(1-b)，第二年的是D1=(NI*b*roe+NI)*(1-b)，股利增长率g=D1/D0-1=b*roe