Market size of newspapers(paper-based) sold in 2040

Your approach looks consistent. The critical point in this problem is estimating penetration in 2040. It is all about which drivers you are providing while you are assuming % of people reading news online vs offline.

- maybe paper usage for newspapers will be 100% banned due to environmental reasons?

- maybe it will be very expensive due to the decreasing number of demand and only very rich people will have this.

etc...

So it is not possible to make a perfect estimation about the last ratio but it is possible to discuss creative and important drivers...

Hope it helps

Best

Serhat

[pop now] * [growth factor to get pop 2040] * [1/# people per household] * [% that reads] * [% that reads new papers] * [% that reads news papers offline]

The last % is the most difficult, This will be low. I would ballpark it at 5%.

The posted formula could work, but really think about that final assumption. Would the paper-based industry still be around if they had only 5% of their readers? They are already struggeling atm and think about all the fixed costs in printing and distribution. 

@ Jorrit: perhaps 5% is too low. Perhaps the industry changes to a niche, more premium offering in which newspapers can charge higher prices.