A retirement plan is built on a set of assumptions that can't be validated until it's too late. One key to successful retirement planning is carefully setting assumptions and revising them often.

Retirement calculations seem so easy. You pick a retirement date. Estimate your living expenses in retirement and choose an inflation rate. You figure out a rate of return for your investments. And then - guess how long you will live. The problem is that your assumptions could be off.

And if they are off by just a little, they could skew the result by a significant amount over your remaining life.

For example, just consider:

The difference between a 5% and 6% return on a

$1 million portfolio over 30 years is more than 1.5 million.

 If your annual living expenses are $60,000 now, in 30 years you'll need an annual income of $147,410 if inflation averages 3%, but just $109,272 if it averages 2%.

Complicating retirement planning further is the idea that one set of assumptions may apply in the beginning, while another set may apply when you reach certain milestones. It seems that the overall inflation rate for older Americans is higher than for the general population. Prices for things that older Americans spend their money on - primarily health care and leisure - are rising by more than the general inflation rate.

When planning your retirement, visualize your life all the way through and establish appropriate assumptions for each phase. We can help you with that. Contact Amy Brandts or Nancy Rick for assistance.

And make plans to attend our Retirement Planning Workshop on September 25. Details below.

Most retirement planning literature portrays a retirement transition in the context of a couple or a family - but what about those who retire alone? Retiring alone presents unique challenges. Singles who retire may lack a spousal and familial support network other retirees count on.

A basic financial truth can't be dismissed: single retirees will need to amass savings comparable to those of a retired couple.

Why? It is because many retirement costs are fixed. Hospitals, universities, banks, pharmacies, mechanics and home improvement specialists do not offer discounts to single parents or lone retirees. Usually, a couple can absorb these costs more effectively than an individual.

Here are some factors to consider.