As the likelihood of a referendum on Britain’s membership of the European Union this year grows, spare a thought for the citizens of Ireland, both north and south.

Most analyses suggest that Ireland would bear a heavier economic cost than the U.K. itself from a British exit, or “Brexit,” from the EU—and would lose out even under the most optimistic scenarios. Yet citizens of the Republic of Ireland—other than the 400,000 residents in the U.K.—will have no say in the referendum. Northern Ireland, meanwhile, comprises less than 3% of the U.K.’s population, giving its voters negligible influence over a decision that could have disproportionate consequences for their prosperity and security.

Dublin has been sounding the alarm for months about its fears for the Irish economy should its nearest neighbor opt to quit the EU. The biggest concern is the potential impact on trade, given the U.K. is Ireland’s largest trading partner. Obviously much depends on the future relationship between the U.K. and EU. But if the U.K. ends up outside the EU single market—which seems plausible given that a vote for a Brexit would be a vote against the free movement of people, which is integral to the single market—then Ireland would be obliged to impose EU tariffs, introduce border controls and customs checks. All of those create obstacles to trade. Ireland’s respected Economic and Social Research Institute predicts Brexit could lead to a 20% fall in bilateral trade.

A Brexit could also impose wider economic costs. Any decline in investment and growth in the U.K. triggered by a British exit from the single market would likely lead to lower Irish growth too, given the close links. There could also be consequences for Ireland’s jobs market. The U.K. has traditionally acted as a safety valve for Ireland’s economy, attracting large numbers of its people during economic downturns. One major uncertainty is therefore whether Irish citizens would continue to enjoy residency rights in the U.K. and access to U.K. welfare. Given the anti-migrant tone of the U.K. debate, that can’t be taken for granted; any restrictions could lead to an increase in Irish unemployment, creating higher costs for the Irish government.

At the same time, Irish businesses worry about the impact of Brexit on their competitive position. A U.K. government freed from the constraints of EU rules might be tempted to use state aid or introduce its own regulatory rules and other non-tariff barriers to give domestic companies an unfair advantage. The U.K. might also open its markets more to third countries, reducing Ireland’s market share. A related concern is the impact of Brexit on the future direction of the EU. Without the UK’s pro-free market influence, the EU might be tempted down a more protectionist path, inflicting new costs on Irish firms that put them at a further disadvantage in global markets.

What about the impact on Northern Ireland? This is hard to quantify since much depends on decisions taken by a post-Brexit U.K. government. The immediate effects on Northern Ireland are likely to be negative given much of the province’s trade goes to the Irish Republic and its largest industrial sector is agribusiness, which is heavily reliant on EU subsidies.

The prospects for the Northern Irish economy would therefore likely hinge on the U.K. government agreeing to at least as generous an agricultural subsidy program as currently provided under the Common Agricultural Policy—and probably more so, should the U.K. exit the single market. The province’s outlook would also depend on London agreeing to pass on any savings on the cost of EU membership to Belfast, assuming those savings weren’t in turn offset by lower tax receipts as a result of any wider hit to U.K. growth.

But the greatest uncertainty for Northern Ireland is about what would happen to the peace process. Dublin strongly believes that EU membership has played a vital role in bringing peace to one of Europe’s most troubled borders. Belonging to the bloc has provided a neutral context in which the two sides could meet as equals, while creating an institutional and legal context for the dismantling of the border to create a genuine all-Ireland market. The generous provision of EU funds has also supported reconciliation and regeneration initiatives. Northern Ireland’s predominantly Catholic nationalist parties share Dublin’s view that any move to reintroduce elements of border control between North and South would be a backward step in the peace process and could be highly destabilizing.

True, Ulster’s traditionally euroskeptic unionist parties are more sanguine, believing the peace process is now sufficiently robust to withstand a Brexit. They are also confident that the Common Travel Area between Britain and Ireland, which predates EU membership, would continue to operate, providing for unrestricted travel across the border.

But this is something that neither the Irish parliament nor the Economic and Social Research Institute believe can be guaranteed. And even leading unionist politicians privately worry about the risk of a breakup of the U.K. should a Brexit vote trigger a new Scottish push for independence. That would reduce Ulster once again to the status of an English colony with all the grim historical baggage that this would entail—something that ought to put the Irish question high on the agenda for all referendum voters, not just the minority who are themselves Irish.