Your Largest Asset Isn't in the Account Ch. 2: You Are Already Overweight Your Own Industry

Investment Background

Diversification is measured across the holdings inside an account. That measurement quietly assumes the account is the whole portfolio. Chapter 1 established that it usually is not — the earnings stream is typically the larger asset. This chapter asks the question that follows immediately: is the largest asset correlated with the second largest?

For a great many people the answer is yes, strongly, in the same direction, and completely unhedged. The correlation between what you are paid for and what you are invested in is the single most common unrecognised concentration in a retirement portfolio, and unlike most risks it is invisible on every statement, every allocation pie chart, and every risk questionnaire.

The Wall Street Translation

The Correlation Nobody Prices

Consider a software engineer at a large technology company holding a total-market index fund, which they were told is the diversified choice.

The index is genuinely diversified across hundreds of companies. But roughly a third of it is technology by weight, and the engineer's salary, bonus, job security and future earning power all depend on the same sector's health. A sustained downturn in technology reduces the value of the portfolio and the value of the career at the same time, for the same reason.

This is not a small effect and it is not theoretical.

In each case the two assets that were supposed to be independent moved together, and moved down. The portfolio needed to be held through a drawdown at exactly the moment the income supporting it became least secure.

Why This Is Worse Than Ordinary Correlation

A correlated portfolio is a problem. A portfolio correlated with your income is a different and larger problem, because it attacks your holding power rather than just your balance.

The standard defence against a drawdown is simply not selling. That defence is funded by income. When income is intact, a forty percent decline is a paper event you can wait out. When the same decline arrives alongside a layoff, the portfolio becomes the thing you have to sell to cover expenses — converting a temporary loss into a permanent one, at the bottom.

This is the mechanism, and it is the reason the chapter exists: the correlation does not merely increase volatility. It removes the buffer that makes volatility survivable. A diversified portfolio and a diversified balance sheet are not the same thing, and only the second one protects you in the case that actually matters.

Division of Labor With the Rest of the Library

The contrast with risk-models-portfolio-construction is the important one. That book is rigorous about correlation and explicitly warns that correlations rise in a crisis. Every input to it is a security. Your salary is not a security, so it never enters the covariance matrix — which means the single largest correlation on your balance sheet is structurally excluded from the tool built to detect correlations.

What This Does and Does Not License

It does not license a bet against your own industry. Shorting your sector, or systematically underweighting it to zero, converts an unmanaged risk into an active position — and an active position taken by someone who is not a professional short-seller, on the sector where their judgment is least detached.

What it licenses is modest, mechanical, and boring: noticing the exposure, declining to amplify it, and preferring the more diversified option at the points where you get a free choice. The correct response to discovering you are already overweight is to stop adding, not to reverse.

Executable Trading Rules

1. Write down your employer's sector, then look up that sector's weight in your main index fund. If you work in technology and hold a US total-market fund, you are carrying sector exposure roughly a third of the portfolio on top of a career fully exposed to it. Knowing the number is most of the work.

2. When you have a genuine choice between two reasonable funds, prefer the one less concentrated in your own sector. A globally diversified fund carries meaningfully less of any single country's dominant sector than a domestic total-market fund. This is a free adjustment, and it is the main practical lever this chapter offers.

3. Size the emergency reserve against the correlation, not against a generic rule. The common advice is three to six months of expenses. If your income and your portfolio fall together, the reserve is doing two jobs at once and belongs at the upper end of that range or beyond — because it is the only asset that is genuinely uncorrelated with both.

4. Never fund a concentrated bet on your own industry with the argument that you understand it. Familiarity with an industry is not an informational edge over the market in that industry, and it is precisely the argument that leads people to double an exposure they already hold.

5. Re-check the exposure when you change jobs, not when markets move. The exposure changes when your employment changes. Market moves change its size; a career move changes its existence.

Relevance to a Retirement Portfolio

The retirement-specific version of this chapter is about sequence, and it is the reason the risk is worth managing rather than merely noting.

The years immediately before retirement are the years of maximum portfolio value and, usually, maximum career-specific concentration — the senior position, the accumulated employer equity, the deep industry specialisation. A sector downturn in that window can reduce the portfolio and end the career in the same quarter, which is the specific scenario retirement-decumulation-mechanics chapter 2 identifies as the retirement red zone. That chapter treats the market half of the problem. This one names the other half: the income that was supposed to bridge a bad sequence may not be there either.

The mitigation is unglamorous and it works: as the portfolio approaches its peak, reduce deliberate concentration in your own sector, keep a larger buffer than the generic rule suggests, and treat employer equity as the concentrated position it is rather than as a bonus. None of this requires predicting anything.

Chapter 3 takes the most extreme version of this correlation — when the company that pays you is also a large holding in your account — and gives it the full treatment it has never received in this library.