Concentration Risk at Ages 40-49: Employer Stock, Winners and Familiarity Bias

Employer Stock: Diversify RSUs as They Vest

At ages 40-49, equity compensation (RSUs, stock options, ESPP) is often a significant source of income and a growing fraction of net worth. The standard guidance is to diversify RSUs on the vest schedule: sell a portion as they vest rather than holding indefinitely. The argument for holding is tax deferral. The argument against is that you already have human capital concentration in this employer (your salary depends on the same company's health). Holding concentrated stock on top of concentrated human capital doubles the single-company exposure in a way that diversification through other assets cannot fully offset.

A practical framework for employer stock: define a maximum percentage of the investable portfolio that can be in any single stock, including the employer. 10% is a common ceiling. If employer stock has grown above that threshold, create a systematic sale plan. Factor in the tax cost of each tranche before executing.

ESPP shares (Employee Stock Purchase Plan) purchased at a discount are a special case. The discount is effectively guaranteed income. Selling immediately after the purchase period locks in the discount without holding period risk. Most financial planners recommend selling ESPP shares shortly after purchase rather than holding them as a long-term investment.

Winner-Position Risk: Trimming as Positions Grow

A position that started at 3% of the portfolio and has grown to 15% through appreciation is now a concentration risk regardless of how it got there. The emotional difficulty is that selling a winner feels wrong: the position has been performing well, and the tax bill is real and immediate. The risk of concentration is theoretical and future.

A rules-based approach removes the emotion: define a maximum single-position limit (5% or 10% of total portfolio), and when a position exceeds that limit, trim back to the target percentage. Execute the trim in tax-advantaged accounts first where available to defer or avoid the taxable gain.

The tax cost of trimming is often the primary objection. A useful way to frame it: would you buy this much of a single stock today with fresh money? If the answer is no, the fact that it appreciated to this concentration does not change the risk profile.

Familiarity Bias: Domestic and Sector Overweights

Familiarity bias causes investors to overweight what they know: their home country, the sectors they work in, and the companies whose products they use. U.S. investors typically hold 70-80% of their equity portfolio in U.S. stocks despite the U.S. representing roughly 60% of global market capitalization at any given time. Investors who work in technology overweight technology stocks. Investors who shop at a particular retailer overweight that retailer's stock.

The antidote is explicit target weights for international exposure and sector exposure set in the IPS, not determined by emotional comfort. A reasonable range for international equity is 20-40% of the total equity allocation. Sector weights above 25% in any single sector (unless that sector represents 25% of the global market) indicate concentration.

Check sector weights annually. If you have more than 30% of your equity allocation in a single sector, examine whether that represents a deliberate view or accumulated familiarity bias. Rebalancing sector weights is typically lower tax cost than rebalancing individual stocks.

Frequently Asked Questions