There are many ways to approach this. If you like targets, then perhaps systematic withdrawal methods might be better for you. In those cases, the only inflation that matters is the inflation that applies to you, personally. Now, you might want to separate your expenses between basic expenses (like utilities, mortgage, insurance, food) and discretion (travel, gifts, etc) and think of the inflation adjusted part as applying only to the basic expenses, for example. That's not to say that you shouldn't shop around for the best deals in those areas (where you can) or move your thermostat setting, etc. But there is a limit even there and you're basically changing the baseline - those items will still be subject to inflation but the point is, each of those expenses have their own price changes over the years. That is, the official CPI is an aggregate of many things, so if you don't purchase those things in the same proportions used by the reported CPI, you're not getting an accurate reading of how your own cost of living is changing. Tracking is the key here.
As noted by many others, however, non-systematic methods work just as well if you're willing (and able) to dynamically adjust your spending during down markets. That becomes tolerable for many if the fixed portion of their income (SS and/or a pension) can supply much of the funds needed for life. Or if your nestegg is big enough that even a small percentage withdrawn per year can still support your basic spending needs.
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