Investment Factor Definitions Compared

Companies that expand their balance sheets aggressively — through acquisitions, capital spending, or share issuance — have historically earned lower average stock returns than companies that grow conservatively. This is the "investment" factor, sometimes labeled CMA (Conservative Minus Aggressive). The idea is simple, but "how much did this company invest" turns out to have several reasonable answers, and academic papers don't all pick the same one.

Three ways to measure "investment"

Total asset growth, used by Fama-French's CMA, is the simplest: the year-over-year percentage change in total assets on the balance sheet. It captures everything — acquisitions, organic capex, inventory buildup, even accounting reclassifications — in one number.

Capital expenditure growth narrows the focus to spending on property, plant and equipment, ignoring working-capital changes and acquisitions. It's a cleaner read on organic reinvestment but misses companies that grow entirely through M&A.

Net share issuance looks at financing rather than spending: how many new shares a company issued (or bought back) over the year. A company can grow assets rapidly by issuing equity to fund expansion, and issuance-based investment factors treat that financing choice itself as the signal, independent of what the cash was spent on.

Worked example

Consider a retailer that opens 200 new stores this year, funded entirely from operating cash flow with no new debt or equity issued. Total assets grow 18% (new stores are assets) and capex grows sharply, so both measures rank it as an aggressive investor. But net share issuance is exactly zero — no new shares hit the market — so the issuance-based factor scores it as neutral, not aggressive.

Now consider a biotech that raises $500 million in a share offering to fund a single acquisition. Total assets jump (the acquired company's assets get added) and share issuance is high, but organic capex barely changes, so the capex-based measure would rank this firm as only mildly aggressive even though the other two measures rank it near the top.

What this means in practice

A quant desk running a multi-factor model needs to be explicit about which investment definition it uses, because the three don't just differ statistically — they flag economically different behavior (spending choices vs. financing choices) that can matter for different investment theses. Vendors and academic replications that disagree on the size of the investment premium are frequently just measuring different things under the same label.