For a financial instrument or financial service, a price normally exists, so one can use quantitative indicators, based on the law of one price, to measure the degree of integration.
In this respect, let me draw your attention to the ECB’s report on “Indicators of financial integration in the euro area” that was published at the end of last month.8 This report provides an assessment of the degree of financial integration in the main segments of the euro area financial market, covering the money market, the government and corporate bond markets, the equity market and banking markets.