Buy-Write Indexes (BXM and Friends)

Definition

A buy-write index is a rules-based benchmark that simulates a covered-call strategy mechanically — no manager, no discretion, no marketing. It "buys" a stock index and "writes" (sells) call options against it on a fixed schedule, following published rules that never change based on anyone's market opinion. The result is a total-return series showing what a plain, systematic covered-call strategy would have earned, decade after decade.

The granddaddy is the Cboe S&P 500 BuyWrite Index, ticker symbol BXM. Its recipe is deliberately simple: hold the S&P 500, sell one at-the-money call option each month expiring in one month, let it settle, and immediately write the next one. That's it. Every month, forever, regardless of headlines or volatility. Because the rules are fixed, the index's long history — computed back through multiple bull markets, crashes, and recoveries — is a clean record of how the covered-call *strategy itself* behaves, separated from any particular fund's fees, execution, or stock picks.

BXM has siblings, each tweaking one rule. BXMD writes calls further out-of-the-money (at roughly a 30-delta strike instead of at-the-money), so it keeps more room for the market to rise before the cap binds — more upside participation, less premium collected. PUT, the Cboe S&P 500 PutWrite Index, is the strategy's cousin: instead of owning stocks and selling calls, it holds cash collateral and sells put options — a position with a nearly identical risk profile that has historically behaved much like a buy-write. None of these are funds you can buy; they are measuring sticks. (The closest investable version of BXM is XYLD, an ETF built to track it.)

If you own a covered-call ETF, a buy-write index is the closest thing you have to an honest answer to the question: is my fund actually adding anything?

Why It Matters

Fund marketing shows you a distribution rate. A buy-write index shows you the pattern — what systematically selling calls does to returns over decades, with no gloss. That long history teaches three lessons that no single fund's short track record can:

• Lower volatility, similar-or-lower long-run total return. Over full market cycles, a

buy-write on an index has historically delivered a meaningfully smoother ride than the index itself, with long-run total returns in the same neighborhood or somewhat below. The premium income is real; the surrendered rallies are equally real.

• It wins flat and choppy periods. When the market goes nowhere, sold calls keep

expiring worthless and the premium is nearly pure added return. Sideways decades are the strategy's home turf.

• It lags bull markets — badly. When the index rips higher, the monthly cap binds again

and again, and the buy-write falls far behind. This is the opportunity cost of the strategy, and the index history shows it is not a fund flaw — it is the design.

The table below sketches the typical behavior pattern across market regimes. The figures are illustrative — rough magnitudes to show the shape, not real index statistics:

That pattern is the whole value of the benchmark. It tells you, before you buy any fund, what the covered-call trade fundamentally is: income and a smoother ride, purchased with upside. Any fund built on this strategy inherits that shape.

The second reason it matters is sharper: the buy-write index is the mechanical baseline an active option-income fund must beat to justify itself. BXM has no manager and no judgment — it is the strategy running on autopilot. If a fund charging an active fee, making strike-selection decisions, and marketing a "dynamic overlay" can't beat the autopilot version on total return over multi-year windows, its process is adding cost, not value. Comparing a fund to the S&P 500 tells you what covered calls cost; comparing it to BXM tells you what the *manager* adds.

Key takeaway: benchmark a covered-call fund twice. Against the plain index, to see the strategy's cost. Against the buy-write index, to see whether the manager earns the fee. A fund can honorably lag the S&P 500 — that's the design — but it should not persistently lag the mechanical version of its own strategy.

Example

Suppose you hold an S&P 500 option-income fund and want to know whether it is doing its job. You pull three five-year total-return figures — the plain index (something like VOO), the buy-write index (BXM), and your fund's NAV total return with distributions reinvested. All numbers below are illustrative:

Read it in two gaps. The index-to-BXM gap (12.0% vs 7.5%) is the price of the covered-call strategy itself over this window — roughly 4.5 points a year of surrendered rallies. If that gap shocks you, the problem is the strategy choice, not the fund; that is exactly the trade described in covered-call opportunity cost.

The BXM-to-fund gap (7.5% vs 6.8%) is the fund's report card. Here the fund landed about 0.7 points a year behind the mechanical baseline — close enough that fees and small execution differences explain it. Now imagine the fund had returned 4.5% instead: a three-point annual shortfall versus autopilot, persisting over five years, is no longer noise. It means the manager's strike choices, timing, or costs are destroying value the plain rules would have kept. Conversely, a fund that returned 8.5% — ahead of BXM with similar volatility — is genuinely earning something beyond the mechanical version.

Notice what this comparison quietly fixed: it stopped judging the fund by its distribution rate. A fund paying 11% and returning 5% is doing worse than one paying 7% and returning 8% — the buy-write benchmark keeps the conversation on total return, where it belongs.

How to Use It as a Holder

You don't need a terminal to use buy-write benchmarks — just a discipline:

1. Match the benchmark to the fund. For S&P 500 covered-call funds (like

SPYI), the S&P 500 buy-write family is the right yardstick. For Nasdaq-100 funds (like QQQI), use the Nasdaq-100 buy-write equivalent — comparing a tech-heavy fund to an S&P benchmark muddies both gaps.

1. Match the flavor to the strategy. An at-the-money writer maps to BXM; a fund that

deliberately writes out-of-the-money or covers only part of the portfolio sits closer to BXMD. Getting the strike style roughly right keeps the comparison fair.

1. Compare NAV total return over multi-year windows. Use the fund's NAV total return

with distributions reinvested — never the distribution rate — over three- and five-year windows that include both a rally and a drawdown. Short windows reward luck.

1. Act on persistent shortfalls, not single years. Any fund can trail its benchmark for

a year. A shortfall that shows up window after window is structural: fees, poor execution, or a payout policy causing NAV erosion. That is the signal to compare alternatives — including the near-mechanical trackers — side by side.

Common Mistakes

• Benchmarking a covered-call fund only against the S&P 500. Of course it lags in bull

markets — that is the strategy, not the fund. The index comparison measures the strategy's cost; only the buy-write comparison measures the fund's skill. You need both.

• Treating BXM as something you can buy. BXM, BXMD, and PUT are calculation

methodologies, not investments. They carry no fees, no trading costs, and no cash drag, so even a perfect tracking fund will trail them slightly. Expect a small gap; investigate a large one.

• Using the wrong flavor of benchmark. Judging an out-of-the-money, partially covered

fund against at-the-money BXM makes it look brilliant in rallies (it kept upside BXM sold). Match the benchmark's strike style to the fund's actual strike selection before drawing conclusions.

• Comparing the fund's distribution rate to the benchmark's return. A buy-write index

reports total return; a fund's headline number is often a distribution rate, which is a payout, not an earning. Put both sides in total-return terms or the comparison is meaningless.

• Reading one hand-picked window. A backtest starting right after a crash flatters the

index; one spanning a flat decade flatters the buy-write. Use several multi-year windows, including at least one full drawdown-and-recovery cycle, before judging either side.

• Assuming decades of index history promise future results. The buy-write pattern —

smoother, income-heavy, rally-lagging — has been persistent, but option premiums shrink when volatility is low. The history is a map of behavior, not a guarantee of magnitude.

FAQ

What is the BXM index?

BXM is the Cboe S&P 500 BuyWrite Index, the original rules-based covered-call benchmark. It simulates holding the S&P 500 while selling one at-the-money, one-month call option every month, rolling systematically forever. Because the rules are fixed and its computed history spans decades, it serves as the standard reference for how a plain covered-call strategy on the S&P 500 behaves — smoother than the index, income-rich, and prone to lagging strong rallies. It is a benchmark, not a fund; the ETF XYLD is the best-known attempt to track it in investable form.

Do covered-call ETFs beat the S&P 500?

Over long, full-cycle periods, the buy-write index record suggests they generally should not be expected to — systematically selling upside while keeping most of the downside tends to produce total returns near or below the index, with lower volatility. Over shorter windows the answer depends on the path: flat, choppy, or falling markets can leave a covered-call strategy comfortably ahead, while strong bull markets leave it far behind. The honest framing is that these funds trade some long-run growth for current income and a smoother ride — a deliberate exchange, not a market-beating scheme.

How do I benchmark an option-income ETF?

Use two comparisons over the same multi-year windows. First, fund versus its plain underlying index — this shows the cost of the covered-call strategy itself. Second, fund versus the closest buy-write index (matching the underlying index and the fund's strike style) — this shows whether the manager adds anything beyond the mechanical version. In both cases use the fund's NAV total return with distributions reinvested, never the distribution rate. A side-by-side comparison tool makes the fund-versus-fund half of this easy; persistent shortfalls versus the mechanical benchmark are the red flag.

What is the difference between BXM and BXMD?

The strike. BXM writes its monthly calls at-the-money — right at the market's current level — which maximizes premium income but caps essentially all upside each month. BXMD writes calls out-of-the-money at roughly a 30-delta strike, leaving room for the index to rise a few percent before the cap binds. BXMD therefore collects less premium but keeps more upside participation. The pair neatly illustrates the central dial of every covered-call strategy: closer strikes buy more income with more surrendered growth.

What is the PUT index?

PUT is the Cboe S&P 500 PutWrite Index, a benchmark that sells cash-secured put options on the S&P 500 instead of owning stocks and selling calls. Financially, a covered call and a cash-secured put at the same strike are near-mirror positions, so PUT has historically behaved much like the buy-write indexes — income-heavy, smoother than the index, capped in rallies. It serves as a second reference point for the same family of option-selling strategies, and as the natural benchmark for put-selling funds.

Can I invest directly in a buy-write index?

No. Like the S&P 500 itself, a buy-write index is a calculation, not a product — it holds nothing and charges nothing. To own the strategy you buy a fund that implements it, either a near-mechanical tracker like XYLD or an active variant such as SPYI or QQQI that layers its own strike and coverage decisions on top. Every real fund adds fees, trading costs, and tracking differences the index doesn't have — which is precisely why the index makes such a useful, unforgiving benchmark for all of them.