Optimal Finance Daily · Friday, August 14, 2026
Darrow Kirkpatrick argues that most retirement calculators are fundamentally broken not because of user interface issues or bugs, but due to deeper theoretical problems. He highlights that simplistic calculations and even those using Monte Carlo simulations often fail to accurately predict future financial outcomes, particularly by ignoring the sequence of returns and current market valuations.
“No, the problems with most retirement calculators are theoretical and go much deeper.”
“It completely ignores the sequence of returns. It assumes that average returns are all that matter. They aren't.”
“The fatal flaw with these calculators then is that they introduce too much randomness, ignoring long-term trends.”