ETF Anatomy

An ETF wraps many stocks into one basket and lists that basket on an exchange. Buy one share of an S&P 500 ETF and you effectively own a slice of all 500 names, in proportion to their weights.

So the first thing to check is never the price chart — it's what's inside the basket and at what weight. Funds with similar names can hold very different things.

Weight is each holding's share of fund assets. A 30% position rising 10% lifts the fund about 3 points by itself. The bigger the weight, the more it drives your return.

Two 'semiconductor ETFs' can be opposites: one stuffing half the fund into two mega-caps, the other spread across equipment and materials names. That difference is where performance gaps start.

Contribution = weight × daily change. A 40% position falling 10% drags the fund about −4 points on its own. Summing every holding's contribution reconciles to the fund's daily move.

A 0.5% position spiking 20% tops the gainers list but barely moves your account. That's why this site sorts by contribution — impact — by default.

HHI sums the squares of each weight — the same index regulators use for market concentration. Roughly: under 1,500 reads diversified, over 2,500 reads concentrated.

Concentrated isn't bad — it's a deliberate bet. The mistake to avoid is holding a 'diversified' fund that is effectively a two-stock portfolio without knowing it.

Buy an S&P 500 fund and a Nasdaq-100 fund and your top holdings are the same mega-caps twice. Combined, your true single-stock exposure is often far bigger than you think.

With multiple ETFs, look at your portfolio at the aggregated stock level, not the fund level. That's exactly what the overlap scanner does.

Leveraged ETFs multiply the index's DAILY move. The catch compounds: if the index drops 5% and recovers to flat, a 2x fund ends about −0.5%, not flat. Chop repeatedly melts it — that's volatility decay.

Loss arithmetic is brutal too: −50% needs +100% to break even; −58% needs +138%. The break-even calculator on every leveraged fund page shows that number as it really is.

Even index ETFs aren't static: index reviews, additions and deletions reshuffle the basket. The stock you bought the fund for may quietly be gone.

The rebalance library detects composition changes across every fund daily and records what entered, what left, and what today would have looked like under the old mix.

Between funds tracking the same index, long-run performance differences mostly come down to expense ratio and tracking error. An annual 0.5% fee compounds into a real dent over a decade.

Comparing fee, size and tracking side by side before buying is simply how ETF shopping should work.

Once you know the holdings, the next question is what price and what profitability they were bought at. Price-to-book compares price against accounting net assets, price-to-earnings against profits, and return on equity measures what that capital actually earns.

The figures shown for a fund aggregate its holdings by weight. Line the three up and the character the name concealed usually surfaces — value or growth, a price supported by earnings or by expectation. Averages hide distributions, though, so always drop down to the holdings to confirm.

Everything here is general financial education, not a recommendation to buy or sell any product. All data on this site is for reference; investment decisions and their outcomes are your own responsibility.