Kevin Crotty
BUSI 448: Investments
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Progressive taxation: income is taxed at higher rates as more is earned
The first dollar earned is taxed less than the last dollar earned.
Marginal tax rate refers to the tax rate owed on next dollar you earn.
Some retirement savings are tax-deductible
Standard deductions vs. itemized deductions
Itemized deductions
Gross Income
-Tax-Deductible Savings Contributions
-Other Deductible Items
=Adjusted Gross Income (AGI)
-Standard or Itemized Deduction
=Taxable Income
We will assume 2 sets of tax rates:
\[FV_1 = \Pi_{t=1}^T \left(1+r_t(1-\tau_{oi,t})\right) \,. \]
\[ \begin{align*} FV_2 =& \Pi_{t=1}^T (1+r_t) - \tau_{oi,T} \left[\Pi_{t=1}^T (1+r_t) - 1\right] \\ =& (1-\tau_{oi,T})\Pi_{t=1}^T (1+r_t) + \tau_{oi,T} \end{align*} \]
\[ \begin{align*} FV_3 =& \Pi_{t=1}^T (1+r_t) - \tau_{cg,T} \left[\Pi_{t=1}^T (1+r_t) - 1\right] \\ =& (1-\tau_{cg,T})\Pi_{t=1}^T (1+r_t) + \tau_{cg,T} \end{align*} \]
A dollar of after-tax investment turns into \[FV_4 = \Pi_{t=1}^T \left(1+r_t\right) \,. \]
After-tax return (after-tax FV/after-tax contribution): \[FV_5 = \frac{(1-\tau_{oi,T})\Pi_{t=1}^T \left(1+r_t\right)}{1-\tau_{oi,0}}\]
If \(\tau_{oi,0}=\tau_{oi,T}\), traditional and Roth IRAs are equivalent on an after-tax basis.
Asset allocation: the choice of how much of each asset to hold
Asset location: the choice of where to locate different asset classes if different tax-advantaged accounts are available.
This is a challenging problem!
Investors with different expected tax rates may come to different allocation and location decisions.
Rule of thumb: Hold more heavily taxed assets (corporate and Treasury bonds) in tax-deferred accounts and lightly-taxed assets (stocks) in taxable accounts
BUSI 448