Why does the Ibbotson Chen risk premium have the expected income component added seprately from the other components?
The other components - expected inflation, gdp real growth and P/E growth are all multiplied geometrically, but expected income is not and instead is added. Why is that so?
Because you are trying to to calculate equity risk premium, which is essentially just (return in equity market - RF rate)
(1xinflation)(1xreal growth rate in EPS) = nominal growth rate in EPS (or real GDP growth whichever you use)
(1xPEg) = nominal change in P/E ratio
nominal growth rate of EPS x nominal change in P/E ratio pretty much gives you what you expect to return in the market. But your return in the market is not complete without accounting for the dividends you will receive + any reinvestment gain you get from those dividends. That is why you add it.
It is like HPR: (P1 - P0)/ P0 = gain you get from capital appreciation + (CF1/P0) = gain you get from cash flow
You can kinda think of it like… HPR = (1xinflation)(1xreal growth rate in EPS) + dividend= return in equity market
Don’t mind me i’m just making stuff up as i go along. This is just how I visualize it though