Introduction
This is a brief introduction to the basic concepts of running ORP.
- Each input form parameter has a help document associated with it.
Click the parameters label (to the left) to see the parameter's help.
- Where appropriate ORP provides for separate accounts for husband
and wife. The accounts appear in two columns, labeled Retiree
and Spouse.
- Retiree's Current Age is required and must be filled in.
- One or more dollar amounts must be filled in, otherwise there
is no plan.
- Except for Retiree's Current Age, all form entries are optional and
may be left blank. ORP supplies a default value for blank fields on
the form.
- Single retirees do not fill in the Spouse column.
- A married retiree with a stay-at-home spouse should still fill
in Spouse's age even though all other values in the Spouse column
will remain blank. Spouse's age is used to compute the term on the plan
if the Term parameter is not set.
- All dollar amounts are in thousands of dollars. For example
$14,000 of annual Social Security benefits is entered as 14.
- A percentage is entered as an interger and fraction. For example
32.5% is entered as 32.5 and not .325.
- Ages are entered as integers.
Model Assumptions
ORP computes a program of cash flows during retirement such that the
total amount of money available for retirement spending is maximized.
To make the model computationally feasible certain assumptions and
simplifications are made. They are presented here:
- The United States Income Tax code will not change:
Given Congress's predilecation for tinkering with the Federal tax code,
this is the most dubious assumption of them all. However, predicting future
Congressional action is beyond the scope of this model. (It should be noted
that ORP is promptly updated when the President signs new tax legislation
that effects retirement issues.)
- Income tax computation:
When computing both Federal and state personal income taxes ORP assumes
that the standard deduction is taken and no itemization occurs.
This implies that state taxes are not taken as an itemized deduction.
Income taxes may be overstated under this assumption because the
retiree may have mortgage interest payments and state tax payments
that exceed the standard deduction.
- After-Tax Account tax rates:
Considerable computational simplification is obtained by treating
the After-Tax Account separately for tax computation.
(ORP computes that taxes for distributions from the Tax-Deferred
Account using the Federal income tax tables for personal income.)
We argue that
most After-Tax Accounts are invested in common stocks and are taxed
at the capital gains rate, computed separately from the personal
income taxes that apply to tax-deferred distributions. Therefore,
loss of accuracy caused by this generalization is minimal.
- Taxing Social Security Benefits:
85% of Social Security benefits are taxable as personal income if
a married couples income exceeds $44,000 ($34,000 for a single person).
A complex computation applies to income of lesser amounts. ORP assumes
that the retiree will have a provisional income in excess of $44,000
and that 85% of Social Security benefits are taxed.
Social security benefits are not subject to state taxation.
- Pensions:
ORP assumes that pensions run the full term of the plan, with no are
related terminated date. Pensions are assumed to remain in full force
even if one spouse dies before the end of the plan.
- Timing of events:
- Disbursments are made from all accounts at the beginning of the year.
- Returns are realized for all accounts at the end of the year.
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© 1998-2006, James S. Welch, Jr.