the return accruing to additional investments is lower than expected, overall ROE will be lower than expected.If the payout ratio decreases, the retention ratio increases.Uto should correctly compute the sustainable growth rate in the mature phase to be $4\mathrm{.}4\%$Uto should correctly compute the sustainable growth rate in the mature phase to be $6\mathrm{.}6\%$Based on the formula for sustainable growth rate, as the retention ratio increases, growth rate increases, holding all else constant.Decline in ROE may lead to a lower growth rate even if the retention ratio increases.