There are several online retirement calculators on the Internet. Many retirement calculators project how much an investor needs to save,.........

There are several online retirement calculators on the Internet. Many retirement calculators project how much an investor needs to save, and for how long, to provide a certain level of retirement expenditures. Some retirement calculators, appropriate for safe investments, assume a constant, unvarying rate of return. Monte Carlo retirement calculators take volatility into account, and project the probability that a particular plan of retirement savings, investments and expenditures will outlast the retiree. Retirement calculators vary in the extent to which they take taxes, social security, pensions, and other sources of retirement income and expenditures into account.

The assumptions keyed into a retirement calculator are critical. One of the most important assumptions is the assumed rate of real (after inflation) investment return. A conservative return estimate could be based on the real yield of inflation indexed bonds offered by some governments, including the United States, Canada, and the United Kingdom. The TIP$TER retirement calculator projects the retirement expenditures that a portfolio of inflation-linked bonds, coupled with other income sources like Social Security, would be able to sustain. Current real yields on United States Treasury Inflation Protected Securities (TIPS) are available at the US Treasury site. Current real yields on Canadian 'Real Return Bonds' are available at the Bank of Canada's site. As of mid-October, 2008, US Treasury inflation-linked bonds (TIPS) were yielding about 2.5%-3% real per annum.

Many individuals use 'retirement calculators' on the Internet to determine the proportion of their pay which they should be saving in a tax advantaged-plan (eg IRA or 401-K in the US, RRSP in Canada, personal pension in the UK). After expenses and any taxes, a reasonable (though arguably pessimistic) long-term assumption for a safe real rate of return is zero. So in real terms, interest doesn't help the savings grow. Each year of work must pay its share of a year of retirement. For someone planning to work for 40 years and to be retired for 20 years, each year of work pays for itself and for half a year of retirement. Hence 33.33% of pay must be saved and 66.67% can be spent when earned. After 40 years of saving 33.33% of pay we have accumulated assets of 13.33 years of pay, as in the graph. In the graph to the right, the lines are straight, which is appropriate given the assumption of a zero real investment return. The lines would be curved if one assumed a non-zero real investment return.

The graph above can be compared with those generated by many retirement calculators. However, most retirement calculators use nominal (not 'real' dollars), and therefore require a projection of both the expected inflation rate and the expected nominal rate of return. One way to work around this limitation is to, for example, enter '0% return, 0% inflation' inputs into the calculator. The Bloomberg retirement calculator gives the flexibility to specify, for example, zero inflation and zero investment return and to reproduce the graph above. The MSN retirement calculator in 2008 cannot be changed from an assumed 3% per annum inflation rate, so one would set an investment return assumption of 3%.

Ignoring tax, someone wishing to work for a year and to then relax for a year on the same living standard needs to save 50% of pay. Similarly, someone wishing to work from age 25 to 55 and to be retired for 30 years till 85 needs to save 50% of pay if government and employment pensions are not a factor, and if it is considered appropriate to assume a zero real investment return. The problem that the lifespan is not known in advance can be reduced in some countries by the purchase at retirement of an inflation-indexed life annuity.


[edit] Retirement calculations