grants and guarantees extended by national agencies of up to 134 bilateral creditor countries and by 56 different international organizations (see Appendix III for a full list). Whenever available we collected data on the creditor and the borrower, both commitment and disbursement amounts, the purpose of the loan as well as the interest rates and repayment terms. In other cases, our data is more aggregate. At the minimum, however, our database contains creditor and borrower country as well as commitment amounts at the annual level allowing us to identify source and direction of official lending and thus the bilateral patterns of international official flows. We now sketch the main sources used in constructing the database.

_International treaty series:_ Our main source for official lending during the 19<sup>th</sup> century and leading up to World War II are international treaty collections. In doing so, we make use of the fact that the conduct of foreign policy became increasingly formalized in the late 18<sup>th</sup> century, so that international loans between two states were now codified in inter-governmental treaties (Keene 2012). Our sources show that, over the course of the 150 years from 1790 to World War II, sovereigns negotiated thousands of bilateral treaties, in which they regulated their political and commercial interactions. To identify bilateral lending, we systematically search the available treaty collections and related databases for bilateral financial agreements that arrange the extension of loans and grants or that extend guarantees on privately issued international loans or bonds.

_National budget accounts:_ For the main bilateral creditor countries, we supplement the information obtained from international treaties with national budget accounts and plans. In particular, we comb through the national budgets of the United Kingdom starting in 1790, France from 1790, Germany from 1870 and the US starting with its first official, foreign loan in 1917. In addition to providing an important consistency check, these sources allow us to capture within-empire (country) transactions, e.g. lending to colonies, for which no inter-governmental treaties exist.

_Reports and datasets from international organizations:_ Starting from the inter-war period, publications and data by international organizations become an additional, highly valuable source. We make extensive use of regular research reports on international capital flows by the League of Nations, the BIS, the IBRD, the UN, the OECD and the IADB. We also use a wide range of creditor specific sources, such as recently declassified CIA reports on foreign lending by Sino-Soviet Bloc countries and the annual reports of a large number of bilateral and multilateral creditor institutions. Moreover, and most importantly, we supplement this hand-coded data with a comprehensive data-extract on bilateral lending from the World Bank's Debtor Reporting System (DRS), which was shared with us on a confidential basis. Specifically, the DRS records all bilateral lending transactions of all member states reporting to the World Bank, starting in the 1960s. For aid flows and grants, our main sources are the 9