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It's a common enough habit: You get a raise, you can suddenly afford to spendmore—and you do.

But if instead of boosting spending each time a raise hit theirpaychecks, workers socked that extra money away into their retirement savings, says a report from Morningstar, they'd be much betterprepared for retirement—in more ways than one.

Higher income, the report points out, can actually make ittougher to prepare adequately for retirement.

Not only do people not generally increase their retirementsavings rate with each raise, that higher income contributes tolifestyle creep—a gradually rising style of living that costs moreand thus is more difficult to maintain on the likely restrictedincome that accompanies retirement.

Retirement assets don't rise at the same rate as income—indeed,if at all—and not only won't keep up with new retirementexpectations, but may even shrink relative to them.

And the higher up the income scale a worker gets, the lesslikely it is that Social Security, in particular, will provide thesame proportion of yearly income that it did at that worker'sformer (and lower) rate of pay, since income provided by SocialSecurity is capped well below the income received by highly paidworkers.

Three savings rules tested for the report were: spend twice youryears to retirement; save your age as a percentage of the raise;and save at least 33 percent of your raise.

In the first instance, someone planning to retire in 10 yearsshould save at least 20 percent of the raise. In the second, a50-year-old should save 50 percent of the raise. And for the third,if a worker's take-home has increased by $1,000, that worker shouldsave $333 of the new income.

Those are just starting points, the report adds, but it can bechallenging to postpone instant gratification in favor ofretirement savings.

Incidentally, the most effective of the three strategies is the"spend twice your years to retirement," while the other two arebetter than the status quo but are only good up to the point whereincome outdistances savings again.

Since this topic isn't often covered in retirement savingsmaterials, workers need a bit more guidance on how much more theyneed to save with each raise to stay on track for retirement.

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