Fire Span
A retirement survival tycoon in 30 shuffled years. Pick a withdrawal rate, steer the allocation, and find out whether your plan dies to bad luck at the wrong time or outlives the deck.
Plan setup
Why order beats average
The deck is the market. Both allocations average a positive year, but the cards arrive shuffled, and the same set of returns in a different order produces a different retirement. Two big down years in the first five, with withdrawals coming out the whole time, can end a plan that would have sailed through the identical years in a different sequence.
The 4% withdrawal figure traces to William Bengen's 1994 study of 30-year retirements, and the 1998 Trinity study found 4 to 5 percent survived most 30-year stretches of US stock and bond history. Both are averages across history, not promises for your order: Bengen's study, the Trinity study.
Fire Span is the playable version of the sequence-risk math behind Firenomics: withdrawal rates are survival questions, not round numbers.