Evidence papers Our Evidence papers offer a summary of the latest literature and research questions in each of our four themes: Cities, State, Firms, and Energy. IGC evidence paper - Cities Gharad Bryan, Edward Glaeser, Nick Tsivanidis Synthesis paper IGC evidence paper - Energy and environment Michael Greenstone, Mar Reguant, Nicholas Ryan, Tim Dobermann Synthesis paper IGC evidence paper - Firms, trade, and productivity David Atkin, Dave Donaldson, Imran Rasul, Matthieu Teachout, Eric Verhoogen, Christopher Woodruff Synthesis paper IGC evidence paper - State effectiveness Oriana Bandiera, Michael Callen, Katherine E Casey, Eliana La Ferrara, Camille Landais, Matthieu Teachout Synthesis paper