Today, global social indicators reach across many societal fields. For example, some deal with good governance and the rule of law, such as the Corruption Perception Index and the various indicators by the World Bank; some with personal rights and economic freedom, such as the World Press Freedom Index and the Global Competitiveness Report; some with human development and political stability, such as the Human Development Index and the Country Risk Index; and some with the performance of commercial and educational entities, such as the UN Global Compact and the various global university rankings.

The contributions of this special issue will specifically focus on the, as-yet underexplored, topic of the legitimacy of global social indicators. This means that we address the meaning of legitimacy and the reasons why some global social indicators may lack legitimacy. We also consider ways to make indicators a legitimate form of governance. Law may have an important role to play in such a process of legitimation; yet, the liquid and transnational nature of global social indicators also presents a challenge to domestic law-makers – and, internationally, of course it may be difficult to find a common approach.

The special issue starts with the paper by Mathias Siems and David Nelken on ‘Global social indicators and the concept of legitimacy’. It explains how legitimacy is commonly understood as both a sociological and a normative concept. It also suggests that indicators, being drafted in a general fashion and based on a quantitative metric, can be regarded as somehow ‘law-like’, thus raising questions about their legitimacy. The paper then addresses these issues of legitimacy, at both the general level of social theory and the operation of indicators in action.

Benoit Frydman's paper on ‘From accuracy to accountability: subjecting global indicators to the rule of law’ goes into further details of the stance of ‘law’ towards global social indicators. It argues that indicators not only convey information, but are genuine tools of global governance and that, for this reason, their legitimacy depends not only on their accuracy, but also on their accountability. Thus, according to Frydman, if indicators are intended to produce or effectively produce regulatory effects, they should be subjected to the rule of law and to judicial review.

Another perspective on ‘law’ and global social indicators is provided in David Restrepo Amariles's paper on ‘Supping with the Devil? Indicators and the rise of managerial rationality in law’. Here the focus is specifically on indicators as managerial devices for driving the legal behaviour of organisations, including those of states and corporations. The paper explores the managerial rationality underpinning such indicators as well as the constraints they convey on legal behaviour. It then relates these findings to the notion of legitimacy, suggesting that legitimacy and reactivity are contingent to their cycle of production and implementation, consisting of data-collecting, benchmarking, auditing and allocating incentives.

Global social indicators are particularly relevant in the context of development policy. The subsequent three papers are therefore more specific in their subject matter, while they also reflect about the legitimacy of indicators at a general level.

Morag Goodwin's paper on ‘The poverty of numbers: reflections on the legitimacy of global development indicators’ identifies indicators as a form of soft power that allows development institutions to set the standards for what, in their view, it is to be developed in the twenty-first century. The paper also explains that they are also not new phenomena. It therefore places global development indicators in their colonial context by focusing on the issue of comparability and the global claim that underpins them.

In Amanda Perry-Kessaris's paper on ‘The re-co-construction of legitimacy of/through the Doing Business indicators’, one of the World Bank indicators is scrutinised under an ‘econosociolegal’ perspective. The paper tracks the ‘re-co-construction’ of the Doing Business indicators within and beyond the World Bank from servant of the private sector and discipliner of states to something approaching social champion. Yet, it also warns that the contested perceptions of legitimacy that have been generated by those indicators may well linger.

The final paper on ‘Fighting global poverty’ by Thomas Pogge presents another critical perspective on a specific set of development indicators. It explains that many different indicators are used to monitor poverty and poverty-related deprivations. The paper discusses the effort to do this by international organisations, such as the World Bank's poverty headcount ratio and the UN's Millennium Development Goals. It also presents an alternative, and possibly more legitimate, way of monitoring deprivation in which the author was involved.

Overall, these contributions show that problems of the legitimacy of global social indicators will remain relevant in the foreseeable future. At least some of the problems of global social indicators are due to power imbalances between drafters and users in general, but also more specifically the risk of biases towards wealthy countries and influential business interests. Depending on the indicator, law may be able to play some role to address these problems; yet, other tools may well be more effective, for example, considering the growing use of technology as a form of governance.

This special issue is an outcome of a workshop held in London in March 2016. We thank the speakers and participants to the workshop. We also thank our universities, King's College London and Durham University for the generous funding of the workshop, and the anonymous peer reviewers for their helpful responses to the papers.