Generative AI assessments remain dominated by frontier capability benchmarks that often fail to capture whether systems can be sustainably deployed, adapted, and trusted in locally grounded and infrastructure-constrained settings. This paper introduces the Next Billion AI Index (nexbax), which we believe is the first diagnostic framework to treat economic viability, operational deployability, and governance alignment as co-equal determinants of AI utility in next-billion-user contexts. Rather than treating usefulness as a single outcome, nexbax operationalizes the preconditions for useful AI through 10 dimensions organized under three themes: Effective Efficiency, Operational Practicality, and Societal Integrity. These dimensions assess whether systems are economically viable, deployable under infrastructure and workflow constraints, and aligned with local needs, user expectations, and collaborative development practices. We pair the framework with rubrics for weak, moderate, and strong performance, and conduct a formative expert evaluation through eleven semi-structured interviews with founders, developers, product leaders, and technical practitioners building AI systems for next-billion markets. Participants found the index useful for reasoning about adoption trade-offs and effective at capturing factors shaping real-world AI uptake -- particularly cost, usability, reliability, and trust. They also identified the need for contextual explanations, domain-specific evidence, and broader stakeholder validation. Nexbax is therefore proposed not as a universal score of social value, but as a diagnostic for artificial useful intelligence: a way to make visible the technical, economic, and governance properties that make inclusive AI deployment more viable.

翻译：生成式AI的评估仍主要受限于前沿能力基准测试，此类测试往往无法衡量系统在本地化部署与基础设施受限环境中能否实现可持续部署、自适应优化及可信赖运行。本文提出"下十亿AI指数（nexbax）"，我们认为这是首个将经济可行性、运营可部署性与治理一致性视为同等关键要素的诊断框架，用于评估面向下十亿用户群体的AI实用性。该框架不将"有用性"视为单一结果指标，而是通过三大主题下的10个维度解构有用AI的先决条件：有效效率、运营实用性及社会完整性。这些维度评估系统是否具备经济可行性、能否在基础设施与工作流约束下部署、是否契合本地需求与用户期望、是否遵循协作开发实践。我们为框架配套了弱/中/强三级评估标准，并通过11场半结构化访谈开展形成性专家评估——受访对象包括面向下十亿市场构建AI系统的创始人、开发者、产品负责人及技术实践者。参与者认为该指数有助于分析采纳决策中的权衡关系，能有效捕捉影响AI实际应用的关键因素（尤其是成本、可用性、可靠性与信任度）。同时他们也指出需要补充情境化解释、领域特定证据及更广泛利益相关者验证。因此，nexbax并非作为社会价值的通用评分而提出，而是作为"人工有用智能"的诊断工具——旨在揭示使包容性AI部署更具可行性的技术、经济与治理特性。