Probability disclosure needs per-rarity specifics, not vague ranges

What it is

Probability disclosure is the core transparency requirement for loot boxes, but "disclosure" quality varies widely: a range like "rare items: 1%-5%" lets players compute nothing about any actual decision (expected pulls to hit the target, the box's real expected value), while itemised rates like "5-star character 0.6%, 4-star character 5.1%, remaining probability split evenly across 4-star items" make expected value computable. Per-rarity disclosure turns probability from a compliance decoration into usable decision information.

Why it happens

Range disclosure fails because it does not change the player's decision inputs. Deciding "should I pull for this character" requires the calculation: target probability × cost per pull → expected spend, compared against one's budget. A range (1%-5%) makes that calculation impossible—the expected-spend interval is too wide to inform (the difference between 50 and 5,000 pulls)—so players fall back on intuitive estimation, and intuitive probability estimation is systematically biased (small probabilities are overestimated), biased precisely in the more-pulls direction. Itemised rates make the calculation possible, and calculation itself has behavioural consequences: a player who knows "expected 147 pulls ≈ ¥2,400" makes a different budget decision from one who feels "should be out in a few dozen pulls." Disclosure's location and format also determine usability—a probability table buried in website announcements is not equally accessible to one reachable in one tap from the purchase screen.

Where it stops holding

Per-rarity disclosure is not full transparency—the probability design itself can be complex enough that disclosure still cannot support decisions: dynamic probabilities (pity rates rising with pull count), multi-pool structures (different banners with different targets), and rates adjusted over time (rerun banners) all distort a static table. Disclosure obligations also have contested edges: whether "rate-up probability" is included in the total rate, whether weapon and character pools need separate disclosure, and whether rates must update in real time when pool contents change—these details decide whether disclosure is nominally or actually transparent. Regulatory trends are moving itemised disclosure from industry self-regulation to legal requirement (China, Japan, and several US states have legislated disclosure granularity), so design teams should treat it as a baseline, not an optional bonus.

Applying it

• Provide one-tap-accessible probability details inside the gacha purchase screen: exact rates per rarity, the item list with each item's share, and the current state of dynamic probabilities (pity progress).
• Offer an expected-value calculator or an "average X pulls needed" display, converting disclosed rates into decision information players can use directly.
• Verification: run a Monte Carlo simulation against the disclosed rates to verify the actual sampling distribution matches (this is a disclosure-truthfulness audit); also audit the entry depth of the probability info (inside the purchase flow versus an external jump).

Related

• Same group: W10.02.1 Loot boxes share gambling's core psychological mechanism · W10.02.3 Pity systems must be explained before purchase · W10.02.4 Visual and audio amplification inflates box-opening excitement and impulse
• Nearby: W10.04 Pay-to-win fairness · O1.01 Trust and transparency · U1.02 Visualising uncertainty
• Search terms: gacha rates · probability disclosure · drop rate · gacha regulation