Justified P/Es are based on firm fundamentals. The leading P/E uses earnings forecasts from the next period while the trailing P/E uses earnings from the previous period. Below we see how we can use the DDM to calculate these ratios.
where:-
P0 = fundamental value
D0 = dividends just paid
D1 = dividends expected to be received in one year
E0 = current earnings
E1 = earnings expected in one year
b = retention ratio
(1 − b) = dividend payout ratio
g = dividend growth rate