Ireland, Malta and Cyprus, three countries with very close historic ties to the United Kingdom, would be particularly deeply affected if the UK chooses to leave the EU, Euractiv.com reports.

S&P’s Brexit sensitivity index sheds light on just how important this close relationship is for certain countries.

The rating agency based its findings on four pillars of the UK’s relations with its EU and international partners: exports, finance, foreign direct investment and migration.

Luxembourg would also feel the full impact of Brexit, due to its heavy reliance on financial services.

But for the three island nations – all former colonies of the British Empire – the negative effects would mainly be felt in higher export costs, as well as potential barriers to direct British investment on their territories, the report said.

The S&P study comes one week after the OECD predicted that Ireland, the Netherlands and Luxembourg would be the hardest hit if the UK chose to give up its EU membership.

After the United Kingdom itself, Ireland, Malta and Cyprus made the most Google searches about the referendum in the last week, ahead of Luxembourg and Switzerland.

Since the beginning of 2016, Malta, Luxembourg and Ireland have also searched for more information on the referendum than any other country outside the UK.