Interpersonal comparability based on functionings
基于功能的人际可比性
Interpersonal comparability becomes much more viable when we focus on functionings vs resources. In the Bergson-Samuelson welfare function, interpersonal comparability is based on resources - e.g., consumption or income. However, since this approach ignores individual characteristics and states of the world, interpersonal comparability can only be based on ordinal measures of welfare.
Under the capabilities approach, interpersonal comparability is based on functionings. We could use a common “basket of functionings” as a basis for interpersonal comparison. In practice, the basket would be based on measurable indicators, such as [Note 1]:
health & demographic indicators - e.g., life expectancy, gender, age, household size;
education level - e.g., schooling, proficiency in reading & writing;
environmental indicators - e.g., geographic location (e.g., urban-rural), availability of public amenities and public infrastructure, level of air pollution;
social indicators - e.g., employment status, ethnicity, income level, social connections (e.g., number of meetings with friends each month).
These indicators assess a person’s ability to convert a given amount of resources into real doings and beings that constitute wellbeing. [Note 2] In the literature on the capabilities approach, “conversion factors” indicate how much functioning one gets out of a given level of resources. The primary conversion factors are personal, environmental and social.
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Reference: Sen 2009, The Idea of Justice
Note 1: In principle, we could specify a set of doings and beings that make up the basket of functionings. However measuring those doings and beings directly would be challenging. Whereas it is feasible to measure an individual’s personal characteristics and her state of the world, leaving each individual to determine for herself the set of functionings that constitute her wellbeing.
Note 2: In comparative international economics, “purchasing power parity” similarly aims to assess living standards based on a basket of goods and services that are typically purchased in a given country. Each country has its own basket of goods and services.
当我们关注功能（而非资源）时，人际可比性变得更加可行。在柏格森-萨缪尔森（Bergson-Samuelson）的福利函数中，人际可比性基于资源 - 例如消费或收入。然而，由于这种方法忽略了个人特征和世界状况，人即可比性只能基于福利的序数度量。
在能力量方法下，人际可比性基于功能。我们可以用一个共同“功能的篮子”作为人际比较的基础。在实践上，该篮子将基于可衡量的指示，例如 [注1]：
健康和人口指示 - 例如，预期寿命、性别、年龄、家庭规模；
教育水平 - 例如，学校教育、阅读和写作能力；
环境指示 - 例如，地理位置（如，城乡）、公共便利设施和公共基础设施的可用性；
社会指示 - 例如，就业状况、种族、收入水平、社会联系（如，每月与朋友见面的次数）。
这些指示评估一个人将一定数量资源转化为构成福祉的实际活动、角色的能力。[注2] 在能力量方法中，“转换因子”表示一个人从给定的资源水平中获得多少能力量。主要的转换因子属个人、环境、社会。
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参考：Sen 2009 《正义的理念》
注1: 原则上，我们可以指定一组构成功能篮子的活动和角色。然而，直接衡量这些功能将具有挑战性。另一方面衡量个体的个人特征和她对世界的状态是可行的，同时让每个人自己决定构成她福祉的功能组合。
注2: 在比较国际经济学中，“购买力平价”同样旨在根据在特定国家通常购买的一篮子商品和服务来评估生活水平。每个国家都有自己的一篮子商品和服务。