Many people can tell you their portfolio balance. Far fewer can tell you what else determines whether their retirement actually works. That's understandable. The balance is the number on the statement. It's concrete, and it feels like a score. But judging retirement readiness by that one figure is a little like judging your health by your weight—useful, and nowhere near the whole story. A framework published in the Journal of Financial Planning offers a wider...

You can do everything right on paper — save diligently, spend reasonably, stay invested for the long haul — and still land in a very different retirement than someone who did the same things. The difference often comes down to a factor many retirement checklists leave out entirely: timing. A lot of advice fixates on a single number: the balance. Have I saved enough? It's an important question. But it assumes that two people who...