Private wealth - including housing assets, bank deposits, stocks, business wealth, but also debt - matters enormously for people’s economic wellbeing and plays a central role in how economies, and potentially even democracies, function. Yet despite growing interest in wealth inequality in both academia and policy circles, many key facts about who owns what and how that has changed over time remain either unknown or contested. Our paper introduces a new data warehouse that brings together information on private wealth, its distribution and its taxation when passed on as an inheritance or gift. The goal is to give researchers better tools to study central questions in social science: What drives the growth of private wealth across countries? Has inequality increased over time? How does tax policy shape the persistence of wealth across generations?

The effort required the collaboration of a large team of researchers across several universities in different countries. We reviewed more than 350 sources: academic research papers, official statistics maintained by central banks and statistical agencies, cross-national survey data, country legislations, and credible grey literature. Where necessary, we derived novel estimates, and we harmonized data across sources, classified different measurement approaches, and supplemented each data point with contextual and methodological information. The result is a curated and extensively documented data warehouse of evidence on private wealth. For example, we offer indicators on the volume of different types of wealth, inequality indicators, and extensive quantitative data on tax codes and features.

 While building a rigorous data warehouse was always the central goal, a major part of our work has been making the data widely accessible. Researchers, students, policymakers, journalists, and members of the general public can explore the data interactively through our online interface at wealthproject.gc.cuny.edu. The site offers pre-built ways to plot data across countries, time periods, sources, and measurement approaches. Users can also inspect the underlying data directly, access methodological documentation, and download customized data subsets.

 The Graduate Center (GC) Wealth Project data warehouse described in the article was initiated with the aspiration to compile the most extensive data source in the field. By offering novel data and by harmonizing existing ones, we aim to facilitate more research on issues relating to the evolution of wealth, its distribution, and tax policy - areas that have previously been constrained by data availability.  We also hope to encourage a more nuanced public and academic debate. Wealth is not only difficult to measure; there are genuinely different ways of doing so, each with its own strengths and limitations. Rather than presenting a single canonical estimate for any given indicator, we deliberately embrace the breadth of available evidence. The data warehouse provides information from multiple measurement approaches allowing users to leverage the power of different perspectives on any given fact.

Looking forward, the GC Wealth Project is a continuous effort to unearth new data and conceive new ways to organise information about wealth. We are also thinking about different ways to expand the scope of the data warehouse. For example, future releases will break new ground, broadening country coverage, not least in Africa, where wealth data is scarcer. In addition, we will provide a new section illustrating the volume of inherited wealth across countries.