2. Language Vitality Index (LVI)

Continuity

A comprehensive "health score" for Kifuliiru that combines how many people speak it, where they use it, and how many generations are actively speaking it.

L V I = \frac{( P _{f} \cdot U _{d} ) + D _{g e n}}{P _{t o t}}

Data & measurement

For Kifuliiru vitality, P_f should come from a defined speaker census or sample; P_tot is the community denominator you are scoring (state it explicitly). U_d is a bounded usage-domain score for Kifuliiru in daily life—keep the 0–10 rubric stable across waves. D_gen counts active generations on the same rule (often 1–5). Avoid double-counting passive recognition as full fluency unless the handbook allows it.

Solution & proof

LVI aggregates (P_f · U_d) + D_gen in the numerator and scales by P_tot for a Kifuliiru-speaking community. The product P_f · U_d rewards both speaker mass and domain breadth; adding D_gen rewards multi-generational use of Kifuliiru. If P_tot grows but numerator is fixed, LVI falls—so pair population estimates with Kifuliiru speaker estimates from the same frame.

Playground

Worked examples and interactive charts now live on their own page.

Open the playground to test sample values, review worked scenarios, and explore how this formula behaves across multiple cases.

Open playground

Variables

Symbol	Description
`LVI`	Language Vitality Index (0 to 1)
`P_f`	Fluent population count
`U_d`	Usage domains score (0-10)
`D_gen`	Generational depth (1-5)
`P_tot`	Total population of the community

Source & tags

Source

ALL_FORMULAS.md — Continuity