Wednesday, November 20, 2013

David Blanchett Develops Simple Formulas and Spreadsheet to Approximate Dynamic Prudent Withdrawal Rate Approach

In Mr. Blanchett's recent article in the Journal of Financial Planning, SimpleFormulas to Implement Complex Withdrawal Strategies, Mr. Blanchett develops "simple" formulas that approximate the results achieved by the more complicated Monte Carlo modeling anticipated in developing Prudent Withdrawal Rates discussed in my post of September 10, 2013.  In addition, Mr. Blanchett further simplifies the process by providing an Excel spreadsheet that enables users to input a few items and develop their own simplified Prudent Withdrawal Rates.  Here is the link to his spreadsheet.

I compared withdrawal rate percentages produced by Mr. Blanchett's spreadsheet assuming 50% equities, total portfolio fees of 0.20% and a 75% Target Probability of Success with the withdrawal rates produced by the Excluding Social Security 2.0 spreadsheet on this site for payment periods of 10, 15, 20, 25 and 30 years (using the recommended assumptons for investment return and inflation), and the results were very close (within .03 percentage points) for payment periods of 30, 25 and 20 and relatively close for payment periods of 15 years and 10 years. 

As mentioned in my September 10 post, I support the dynamic "actuarial" approach proposed by Messrs. Frank Sr., Mitchell and Blanchett, and I believe that Mr. Blanchett's simplification is a very useful addition to make their approach more accessible to financial planners and other users.  

I will point out that Mr. Blanchett's spreadsheet is most useful to a retiree who has no other sources of retirement income or bequest motives as it does not coordinate with other sources of retirement income, such as annuities, and it does not provide for leaving a specific amount to heirs.  To reflect such items, you may have to use their more complicated model, or the simple spreadsheet set forth in this website.