[nshelly]

Princeton's current 2018 size is $25.9B. In 2001 it was $8.4B, so a annual growth rate of over 6% per year.

So Princeton would have to spend 1.6% of their endowment every year to offer free tuition to their students. Assuming their rate of return on the endowment (including alumni contributions) can grow faster than the cost of tuition growth, they can provide free tuition for their students indefinitely.

[ChrisLomont]

Princeton tuition was 26K in 2001. It is now 45K. That's 3% growth in tuition, cutting into your estimate.

The current growth is already being spent to fund the university to the tune of ~4-6% [1].

So, if you take that source away, tuition would likely have to pick up the slack.

Care to rerun your numbers adding this all in?

[1] https://www.princeton.edu/news/2013/10/18/princeton-endowmen...