Did you understand what is the worst sustainable spending rate? Do they mean by spending financing current needs ? If yes, how does it correlate to the risk of not being able to accumulate the target amount at the horizon date ? As they explained it’s not enough to consider the risk that portfoilo value’ll be insufficient at the end of long horizon, we also need to consider the risk that occur prior to the horizon date. And they suggested to use the worst sustainable spending rate that occur prior to the horizon. If by spending they mean current spending expenses: let’s assume we have a goal to save money for retirement in 10 years. Considering the worst sustainable spending rate we control the risk that principal capital amount’ll be lost for financing current expenses But if we have a goal to earn money for retirement how will the worst sustainable spending rate help us ? Let us assume that we chose inv. portfolio with the worst sust.spending rate that satisfies our needs for covering the current expenses. But even if we control the risk that prior horizon date we won’t be able to cover our current expense without running out our capital it doesn’t mean that we consider the risk that investment return will be sufficient to accumulate the needed amount in 10 years…