He is an Associate of the Center for the Study of Civil War at the Peace Research Institute Oslo.

He has also worked with data on anti-smoking regulations, student satisfaction and attainment, foreign direct investment, exchange rates, and the mitigation of natural disasters including gender differences.

He is the author of four books: Weak versus Strong Sustainability: Exploring the Limits of Two Opposing Paradigms (4 editions),[2] The pattern of aid giving: the impact of good governance on development assistance,[3] and Greening trade and investment: environmental protection without protectionism.

[4] Robustness Tests for Quantitative Research (with Thomas Plümper) was published in 2017.

Together with Giles Atkinson and Simon Dietz, he is the editor of the Handbook of Sustainable Development.