--- title: "What Is a Base Rate in Forecasting?" term: "Base rate" type: glossary_term canonical: https://www.moonwire.org/insights/glossary/base-rate.html --- # What Is a Base Rate in Forecasting? > How often an event happens in general, before looking at any specific evidence. In forecasting it is the starting point, and the naive benchmark any real forecast has to beat. A **base rate** is the underlying frequency of an event across a relevant history — the answer to "how often does this happen, usually?" before considering anything about the current situation. If a coin in a basket has closed higher over a seven-day window 56% of the time, its seven-day up base rate is 56%. ## Why it comes first Specific evidence feels more persuasive than general frequencies, so people tend to underweight base rates — a well-documented error known as *base-rate neglect*. A story about why an asset should rise this week can be compelling while telling you almost nothing beyond what the base rate already did. Starting from the base rate and then asking how far the evidence justifies moving away from it is the discipline that keeps forecasts honest. ## The base rate as a benchmark A forecaster who knew nothing about the current market could still forecast the base rate every time. That naive strategy sets the bar: - If a set of forecasts cannot beat the base rate, it is not adding information, however sophisticated its reasoning. - Comparing a [Brier score](https://www.moonwire.org/insights/glossary/brier-score.md) to the base-rate forecast's Brier score gives the [Brier skill score](https://www.moonwire.org/insights/glossary/brier-skill-score.md). In crypto this matters more than it sounds. Over many historical windows the major assets rose more often than they fell, so a forecaster who always says "up" can post a respectable hit rate without any insight. A headline accuracy figure means little until it is placed next to that naive number. ## Choosing the right base rate The base rate depends on the question: the horizon (seven days is not thirty), the asset, and the period measured. A base rate built on a bull-market sample will overstate how often prices rise in general. Stating which history a base rate comes from is part of reporting it. ## In MoonWire analysis Each [prognosis](/insights/prognosis-daily-2026-09-09.html) call is issued with the engine's probability *and* the base rate beside it, and the published record scores the engine against the base-rate forecaster on the same calls. A call only goes out when the evidence clears a conviction gate relative to that base rate. ## Further reading - [Wikipedia: Base rate](https://en.wikipedia.org/wiki/Base_rate) - [Wikipedia: Base rate fallacy](https://en.wikipedia.org/wiki/Base_rate_fallacy) ## Where this appears in MoonWire analysis - [Prognosis daily - rotation holds, three slots stay open, and the one call we refused](https://www.moonwire.org/insights/prognosis-daily-2026-09-09.md) — Sep 11, 2026 - [Prognosis daily - 29 Aug: one fresh Solana lean, the rest of the book left running](https://www.moonwire.org/insights/prognosis-daily-2026-08-29.md) — Sep 11, 2026 - [Choppy holds, breadth splits down the middle, and two calls resolve against us](https://www.moonwire.org/insights/prognosis-daily-2026-08-16.md) — Sep 11, 2026 - [Week-ahead read: a thin news window, a choppy tape, and four calls that all landed](https://www.moonwire.org/insights/prognosis-daily-2026-08-09.md) — Sep 11, 2026 - [Macro takes the wheel: a weak jobs print, an unchanged policy rate, and a tape that keeps thinning](https://www.moonwire.org/insights/prognosis-daily-2026-08-08.md) — Sep 11, 2026 --- *MoonWire surfaces and summarizes public crypto news.* **General information only — not financial advice.** MoonWire Ltd. is not licensed by ASIC and holds no AFSL. This content does not consider your objectives, financial situation, or needs, and is not a recommendation to buy, sell, or hold any asset. *This analysis is generated by artificial intelligence and may be inaccurate, incomplete, or fabricated. Independently verify before acting.* © 2026 MoonWire Ltd. · [Terms](https://www.moonwire.org/legal/TOS) · [Risk Disclosure](https://www.moonwire.org/legal/RISK_DISCLOSURE) · [Privacy Policy](https://www.moonwire.org/legal/PRIVACY_POLICY)