The Would-I-Buy-It-Today Test

Quick answer

The would-I-buy-it-today test asks: if you held cash equal to your current position's value right now, would you buy this same stock at today's price and at this size? A clear no is a sell signal worth investigating. The test works by resetting the frame, stripping out cost basis and purchase history so you evaluate the position on its forward merits alone.

Why cost basis creates anchoring bias

Cost basis is the price you paid to enter a position. It is a fact about the past. It has no bearing whatsoever on what the position will return going forward. The future performance of any stock is determined by its underlying business fundamentals, its current valuation relative to those fundamentals, investor flows, and the macro environment, not by the number at which you happened to buy in.

Despite this, investors routinely use cost basis as the reference point for sell decisions. The most common manifestation is the instinct to "wait until it gets back to what I paid." A position bought at $90 that has fallen to $70 is evaluated against the $90 entry price rather than against the current $70 value and what it is likely to be worth in 12 to 24 months. The $90 is gone. The $70 is the capital you have. The question is what happens to the $70 from here, and that question has nothing to do with the $90.

This is anchoring bias as described in behavioral economics research by Kahneman and Tversky: when making estimates or decisions under uncertainty, people over-rely on an initially presented piece of information, even when that information is irrelevant to the decision at hand. In investing, the initial purchase price is the anchor. It feels like a benchmark because it is personal and memorable, but it is not analytically relevant.

The practical consequence of anchoring to cost basis is that investors hold losing positions longer than they should and sell winning positions earlier than they should, a pattern documented across retail and institutional investing. Both behaviors are the opposite of optimal. Losers should be evaluated on whether the thesis still holds at the current price. Winners should be evaluated on whether the current price still offers adequate forward return. Neither evaluation requires the original purchase price.

How the test resets the frame

The would-I-buy-it-today test is a thought experiment designed to eliminate the anchoring distortion. The premise is simple: imagine that instead of owning your current position, you hold cash equal to its current market value. Now ask whether you would choose to invest that cash in this exact position, at today's price, in the same quantity you currently hold.

Rephrasing the question this way changes the psychological frame in three important ways.

First, it shifts the evaluation from "should I sell?" to "should I buy?" Research on the disposition effect (Shefrin and Statman, 1985) found that investors are generally more willing to sell winners than losers, in part because selling a winner feels like a success and selling a loser forces an acknowledgment of a mistake. The would-I-buy-it-today framing sidesteps this asymmetry entirely by making both scenarios feel like fresh allocation decisions.

Second, it forces a current-price analysis. When you ask "should I sell?", the natural tendency is to think about the position's history: where it was, where it went, what you hoped for when you bought. When you ask "would I buy this today?", the analysis necessarily starts at today's price and looks forward. This is the correct analytical frame for any hold-or-sell decision.

Third, it incorporates size. The question is not just "would I buy some of this?" but "would I buy this much of this?" A stock that you would happily hold as a 3% position might not pass the test as a 9% position that resulted from a price run-up. Position sizing at the current price and current portfolio weight is part of the evaluation, not an afterthought.

Running the test on a real holding: step by step

Applying the test in practice requires more than asking the question and answering intuitively. A structured approach produces more reliable results.

Step 1: State the current thesis in one paragraph. Before asking whether you would buy, write down what the thesis for the position is right now, based on current information. Not the thesis you had when you bought. The thesis that would justify buying today. If you cannot write a clear, current thesis, that inability is itself a signal.

Step 2: Identify what would need to be true for the thesis to work. What are the two or three critical assumptions that underpin the current case for the stock? Are those assumptions still intact? Have any of them been materially weakened by recent information?

Step 3: Assess the current setup. At today's price, what does the expected return look like over your intended holding period? Use a simple scenario framework: bull, base, and bear outcomes with assigned probabilities. Compute a weighted expected return. Is it competitive with your opportunity set?

Step 4: Evaluate the position size in context. Does the current portfolio weight of this position reflect your conviction level and its contribution to overall portfolio risk? A position that grew from 4% to 8% of the portfolio through price appreciation may now be larger than your conviction level supports.

Step 5: Answer the question honestly. Given the current thesis, the current price, the expected return estimate, and the portfolio weight, would you deploy fresh cash here today? If yes, hold. If no or uncertain, move to the diagnostic phase to determine whether a trim or exit is warranted and, if so, what alternative deserves the capital.

What "no" actually means and what to do next

A "no" answer to the would-I-buy-it-today test is not an automatic sell. It is a flag that initiates a structured review. The nature of the "no" drives the appropriate response.

If "no" because the thesis is no longer compelling: this is a thesis-break or thesis-softening situation. The position may need to be exited regardless of what else is available in the opportunity set. You would not buy this fresh because the original reason for owning it has weakened or disappeared.

If "no" because the price now fully reflects fair value: this is a valuation sell trigger. The position is not broken, but the forward return at the current price is too low to justify the allocation. You would not buy it fresh because there is little return left to capture.

If "no" because something else is materially more attractive: this is the pure opportunity-cost case. The position may still have a valid thesis and reasonable forward return, but another candidate offers better expected returns per unit of risk. The capital should migrate toward the better opportunity.

If "uncertain" or "reluctantly yes": this intermediate answer often signals that the position has become a comfort hold rather than a conviction hold. It is not broken and not obviously beaten by something else, but you are holding it partly out of inertia. These positions benefit from a formal review with explicit criteria for what would change the answer to a confident yes or a clear no.

When the test is most useful

The would-I-buy-it-today test is most valuable when run at predictable intervals rather than only when a position is in trouble. Three timing contexts produce the best results.

Quarterly staleness reviews. Run the test on every position once per quarter regardless of recent performance. Positions that have been in the portfolio for several quarters without a clear catalyst deserve particular scrutiny. The test surfaces whether you are holding them by analytical conviction or by default.

After a significant price run-up. When a position appreciates 40%, 60%, or more, the forward return math changes materially even if the business has not changed. A company trading at 15x earnings offers a different expected return than the same company trading at 25x earnings. The test at the new price forces a reassessment of whether the allocation still makes sense at the current valuation.

After a macro or sector regime change. Interest rate cycles, regulatory changes, commodity price moves, and technological disruptions can alter the attractiveness of entire categories of holdings. A position that was well-positioned for one environment may be neutral or unfavorably positioned for the environment that follows. Running the test after a significant macro shift catches positions whose thesis was implicitly conditional on the old regime.

Documenting the test in a decision journal

A decision journal is a written record of investment decisions and the reasoning behind them at the time they were made. Applying the would-I-buy-it-today test consistently is more valuable when the results are documented, for two reasons.

First, writing forces specificity. An investor who runs the test in their head can remain vague about why the answer is yes or no. An investor who writes down the answer must articulate the thesis, the key assumptions, and the expected return estimate. That specificity makes the review more rigorous and catches errors in reasoning that informal thinking misses.

Second, documentation creates accountability. When you run the test on the same position three quarters in a row and record "uncertain" each time without acting, that pattern is visible in the journal. It prompts the question: why are you continuing to hold a position you have repeatedly assessed as uncertain? The answer might be a legitimate one (tax timing, liquidity constraints), but it should be an explicit answer rather than an unexamined default.

A minimal journal entry for a would-I-buy-it-today test review includes the position and current weight, the date, the current thesis in two to three sentences, the key assumptions, a rough expected return range, the answer to the test question, and the action taken or deferred and why.

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