How the indices work

Every index follows the same published, mechanical rules. This page explains those rules end to end, answers common questions, and defines the terms used across the site.

Methodology, step by step

Selection. Each index has an explicit rule for what belongs in it — for example, the 100 most valuable retired sets, or every set within a given theme. The rule is stated on the factsheet and applied without exception.
Pricing. Constituents are valued from BrickLink secondary-market data, BrickLink-first and US-scoped. We prefer the quantity-weighted average of recent New sales; when sold data is thin we fall back to the trimmed median of the few lowest current US New listings (widening to North America, then worldwide, only if none are closer), so VAT- and shipping-inflated international asks don’t distort the figure. To keep quotes honest a set needs at least two active listings to enter an index, while an existing constituent may remain on a single listing so a genuinely scarce set isn’t churned out the moment its lone listing lapses.
Weighting. Indices are price-weighted: each constituent's share of the basket is proportional to its price, so more valuable items move the index more. This mirrors the classic Dow construction.
Rebalancing. Baskets are refreshed monthly. Constituents that no longer meet the rule drop out; newly eligible items enter. A divisor adjustment keeps the level continuous across rebalances so changes reflect the market, not the reshuffle.
Base level. Each index starts at 1,000 on its inception date. A level of 1,250 means the basket is up 25% since inception.
Inflation adjustment. Returns are shown in both nominal and real (inflation-adjusted) terms using BLS CPI-U, so growth can be separated from the general rise in prices.
Modeled history. For months before an index went live, levels are modeled from available historical value estimates and clearly shaded as modeled on the charts. Everything from the live inception date forward is computed from stored month-end snapshots.

Frequently asked

Are these securities, or can I invest in an index?

No. These are informational benchmarks, not funds or securities. There is nothing to buy, and nothing here is investment advice.

Why price-weighting instead of equal-weighting?

Price-weighting reflects how the market's value actually concentrates — a few high-value sets carry real weight. It is transparent and easy to reproduce from the published constituent prices.

How current are the prices?

Constituent set prices are refreshed daily from BrickLink, so the live value behind each index tracks the market day to day. Published index levels are still locked to a monthly close (the “as of” date on each factsheet marks the latest month reflected), so the official series stays clean and reproducible while the underlying prices stay current.

How current are the traditional benchmarks (S&P 500, gold, Bitcoin)?

The traditional benchmarks quote roughly every 15 minutes while the site is awake, pulled from public market data. They’re shown purely for apples-to-apples comparison against the LEGO indices and are not part of any LEGO index.

Why does a set's value differ from what I see elsewhere?

Secondary-market prices vary by source, condition, region, and timing. We document our pricing rule so any figure can be traced back to how it was derived.

Glossary

Index level: The single number tracking a basket, rebased to 1,000 at inception.
Constituent: An individual set or minifigure that is a member of an index.
Price-weighting: A weighting scheme where each constituent's influence is proportional to its price.
Rebalance: The monthly process of refreshing an index's membership and weights against its rule.
Nominal vs. real: Nominal is the raw change; real strips out inflation (via CPI-U) to show purchasing-power change.
CAGR: Compound annual growth rate — the smoothed annualized rate of change over a period.
MSRP: Manufacturer's suggested retail price — the original launch price, used as a baseline for returns.
Part-out value: The estimated value of a set if sold as individual parts and minifigures.

Nothing on this site is investment advice, an offer, or a solicitation. Figures are informational estimates derived from third-party data and may contain errors.