##isation, indicators of international financial trade increased from the early 1990s until the global financial crisis and have subsequently stabilised since then in proportion to global output ( chart 4 ). as shown in my work with gian maria milesi - ferretti, the expansion in external assets was concentrated in positions vis - a - vis international financial centres, which in turn are linked to the corporate structures of mnes. chart 4 evolution of external assets ( percentages of world gdp ) sources : external wealth of nations database ( lane and milesi - ferretti ) and ecb staff calculations. notes : aggregates for advanced economies, financial centres and emerging and developing countries are defined as in lane, p. r. and milesi - ferretti, g. m. ( 2018 ), “ the external wealth of nations revisited : international financial integration in the aftermath of the global financial crisis ”, imf economic review, vol. 66, no 1, international monetary fund, pp. 189 - 222. gross foreign direct investment ( fdi ) transactions of euro area countries with financial centres have been so large that these have driven aggregate euro area developments. euro area fdi also exhibits a strong correlation between gross assets and liabilities, especially in financial centres, which points to the importance of the pass - through of financial flows for the evolution of fdi data. the challenge in interpreting headline fdi data is further compounded by the large presence of spes in a number of euro area countries. spes account for sizeable shares of cross - border financial transactions and positions in fdi. statistics on spes, however, remain underdeveloped, since these do not follow a harmonised international definition and data are systematically collected only for a limited set of countries. the limitations of cross - border statistics also make it difficult to analyse properly international financial exposures. [ 8 ] although data on international financial transactions and positions have improved significantly over the past decade ( in terms of coverage and details available on instruments, sectors and geographic breakdowns ), visibility on the links between ultimate investors and ultimate issuers of financial instruments remains limited. [ 9 ] the identification of ultimate exposures has been further complicated in recent years by the expansion of international financial intermediation chains, which often involve nonbank entities located in international financial centres. [ 10 ] a good example of this is the difficulty in measuring foreign currency exposures in international balance sheets – for which official statistics remain sparse – although research - based data

3. see lane, p. r. ( 2017 ), “ the treatment of global firms in national accounts, ” central bank of ireland economic letter no. 2017 - 1 ; avdjiev, s., everett, m., lane, p. r. and shin, h. s. ( 2018 ), “ tracking the international footprints of global firms ”, bis quarterly review, bank for international settlements, march ; also lane, p. r. ( 2020 ), op. cit., and di nino, v., habib, m. m. and schmitz, m. ( 2020 ), “ multinational enterprises, financial centres and their implications for external imbalances : a euro area perspective ”, economic bulletin, issue 2, ecb. 4. see lane, p. r. ( 2020 ), op. cit. 5. see pastoris, f. and schmitz, m. ( 2020 ), “ box 5 euro area - us current account asymmetries : the role of foreign direct investment income in the presence of multinational enterprises ”, economic bulletin, issue 2, ecb. 6. see lane, p. r. and milesi - ferretti, g. m. ( 2018 ), “ the external wealth of nations revisited : international financial integration in the aftermath of the global financial crisis ”, imf economic review, vol. 66, no 1, international monetary fund, pp. 189 - 222 ; and mcquade, p. and schmitz, m. ( 2017 ), “ the great moderation in international capital flows : a global phenomenon? ”, journal of international money and finance, vol. 73, pp. 188 - 212. 7. see also di nino, v. and a. ekstam ( 2020 ), “ what value added in the trade balances of euro area financial centres?, ” ecb working paper series, no. 2506. 8. see lane, p. r. ( 2015 ), “ risk exposures in international and sectoral balance sheet data ", world economics, vol. 16, no 4, pp. 55 - 76. 9. see galstyan, v., lane, p. r., mehigan, c. and mercado, r. ( 2016 ), “ the holders and issuers of international portfolio securities, ” journal of the japanese and international economies, vol. 42