On June 23, the United Kingdom will hold a referendum to determine whether or not it will remain a member of the European Union. The highly contentious vote has been dubbed by international media as “Brexit” (Britain’s exit from the EU).

The UK, like France and Germany, is a net contributor to the EU, meaning that it pays more into the EU than it receives from it. The money that wealthier states pay in membership fees is redistributed to poorer members like Greece for infrastructure and economic development. Critics argue that membership in the EU is an undue financial burden on the UK given this scenario— as Britain’s economy improves, it must pay for a greater portion of the EU’s budget.

“Euroskeptics” believe that membership in the EU hampers the UK’s ability to conduct international trade on its own terms, and that an independent UK would be able to create its own trade agreements with foreign nations such as China. Supporters of “Brexit” cite the success of Norway, which has access to the single market of the EU but is not subject to its economic regulations.

Citizens of the European Union are free to move throughout its 28 member states. In recent years, thousands of Eastern Europeans— especially those from former Soviet bloc states like Romania and Poland— have arrived in the UK looking for blue collar work. Many British blue collar workers feel threatened by this significant influx of legal migrant workers, and hope that an independent UK could enforce stricter immigration laws. Furthermore, the recent terrorist attacks in Paris and Brussels have sparked fears that unrestricted movement throughout Europe could increase the likeliness of attacks in major British cities.

The International Monetary Fund (IMF) warns that Brexit could have severe negative effects on the British economy. Recent data from a London-based think tank suggests that Britain’s departure from the EU could decrease its gross domestic product (GDP) by anywhere from 1% to 9%.

Economic repercussions could be felt in the US and elsewhere.  London rivals New York as the investment capital of the world, but investment could decline due to fears of economic uncertainty. American investment could also decrease if the UK is no longer seen as a gateway to the EU single market.

The UK is a major force of security and stability in Europe. Its strong economy creates a balance within the EU and prevents German economic dominance. EU membership also strengthens both the UK and the EU’s leverage in international diplomacy, which is crucial given that Europe is faced with an increasingly bellicose Russia and the most severe refugee crisis since World War II.

Brexit could undermine American foreign policy interests. European integration has been a cornerstone of US foreign policy since the beginning of the Cold War, as it has prevented the recurrence of disastrous conflicts similar to the two World Wars and led to successful trade and military agreements (such as NATO). In particular, the “special relationship” between the US and the UK provides the US with a key ally in the EU and in projects in the increasingly volatile Middle East. Britain leaving the EU could trigger a domino effect, in which various member states follow the UK’s lead and European stability would disintegrate.

EU membership actually decreases the likelihood of terrorism in the UK, as it facilitates the exchange of intelligence and criminal records.

The Financial Times’ Brexit poll tracker states that as of May 8, 2016, 46% of respondents chose “stay,” 43% chose “leave”, and 11% are undecided. While a majority responded in favor of staying in the EU, the undecided voters could possibly tip the scales in favor of Brexit.