Enlightenment Economicsなる会社を率い、最近下記の本を出した英国のフリーランスの経済学者Diane Coyleが、先月「Measuring economic progress」と題した記事をvoxeuに寄稿しGDPやその代替指標について論じている(H/T Mostly Economics)。

GDP: A Brief but Affectionate History

GDP: A Brief but Affectionate History


One of the key questions debated in the 1930s concerned the aim of a single headline indicator of the economy as a whole. Should it measure social welfare, or should it instead just measure the level of activity? Simon Kuznets, often misleadingly described as the father of GDP, argued in favour of the former, but the needs of wartime production settled the debate in favour of an activity measure: GDP.

Economists have always been aware that GDP does not measure welfare, but in practice its growth has come to be widely used as the general litmus test for the health of the economy, both in the economic literature and in the media and public policy debate. So it is not surprising that the tension between measuring welfare and measuring economic growth has re-emerged several times over the decades since World War II.
1930年代に良く議論された重要な問題は、経済全体についての単一の総合指標の目的についてであった。それは社会厚生を測定すべきなのか、それとも単に経済活動の水準を測定すべきなのか? GDPの父と良く誤解されているサイモン・クズネッツは前者を支持したが、戦時生産の必要性が活動指標を支持する形で議論を決着させた。それがGDPである。



However, one flaw of the single alternative indicators is that they all omit positive contributions to welfare that are not captured in the GDP statistics either. Despite the use of hedonic price indices to capture some of the quality improvements in a range of goods such as computers or housing, GDP understates – probably to a large degree – the increases in consumer welfare due to quality improvements, new goods, and increased choice. Even apparently trivial innovations such as a novel flavour of breakfast cereal seem to have led to large gains in consumer welfare (Hausman 1996).
A further flaw is that the alternatives to GDP obscure the conceptual distinction between activity and welfare, and all involve an implicit weighting of the different dimensions of welfare. For some purposes – macroeconomic policy for one – an activity indicator is essential. What’s more, the prominent alternative indices do not all rest equally firmly (if at all) on an explicit theory of social welfare; for example, the components of the GPI and the components of the widely-used Human Development Index differ greatly because of the choice of component indicators. Finally, a single welfare indicator obscures unavoidable trade-offs between components. The most obvious trade-off is that between income and what is often called ‘work-life balance’, or in other words the amount of leisure.
それら代替指標の共通の欠点は、GDP統計で捉えられていない厚生へのプラスの寄与を同様に省略していた、という点にあった。GDPは、コンピュータや住宅といった種類の財の質的向上を捉えるためにヘドニック物価指数を用いてはいるものの、質的向上、新製品、ならびに選択肢の増加による消費者厚生の上昇を――おそらくはかなりの程度――過小評価している。朝食用シリアルの新しいフレーバーといった一見些細なイノベーションでさえ、消費者厚生の大きな利得をもたらしたものと思われる(Hausman 1996)。


The other issue obscured by proposed alternatives to GDP is the question of sustainability. Although this is clearly a contributor to social welfare, combining sustainability indicators into a single index along with indicators of current activity and welfare obscures another important set of trade-offs made between present and future consumption. GDP itself has this flaw, making no distinction in the aggregate measure between current consumption and investment. But it is impossible to assess sustainability without making a number of assumptions about the future: what is growth in the interim likely to be? What might be the possible technological innovations? How might people’s behaviour change in response to changing prices, technology and incomes?

Given the uncertainty about these questions, a partial indication of sustainability is given by the current change in net national product, which has the advantage of being derivable from currently available statistics. However, it omits some crucial aspects of sustainability, notably natural assets.

この記事のCoyleは、単一の総合指標ではなく、OECDのBetter Life Indexのように、指標を一覧する方式(dashboards of indicators)に可能性を見出しているようである。それは、トレードオフが明示的に示されている、利用者が好きなウエイト付けができる、という利点を持っている、とCoyleは言う。


The book ends by making the case that GDP was a good measure for the twentieth century but is increasingly inappropriate for a twenty-first-century economy driven by innovation, services, and intangible goods.