Britons will go to the polls on June 23 to decide whether the U.K. should stay in or leave the European Union. Uncertainty over the global economy is mounting over the upcoming “Brexit referendum.”

The percentage of the proponents of the departure is estimated to hover around 40 percent in the U.K., while the ratio of opponents slightly exceeds it.

If Brexit becomes reality, South Korea is certain to face aggravated difficulties in its export performance that has already taken a big hit. This would mean that Asia’s fourth-largest economy could face a longer-than-expected economic slowdown.

The size of the blow that Brexit would deal can be seen from previous reports on the impact on the Korean economy of Greece’s exit from the eurozone, which is still posing a threat to the global economy as a lingering possibility.

The Korea Economic Research Institute predicted last year that Grexit would slash Korea’s GDP growth by up to 2.7 percentage points compared to business as usual. The benchmark KOSPI was also expected to plunge about 20 percent.

The assessment indicates that Korea’s yearly growth could stay around zero or face a recession and the stock price index could nosedive to 1,600 points. The report also said that capital flight would come to more than 14 trillion won ($11.8 billion) under a Grexit.

Greece is the world’s 46th-largest economy and the U.K. is ranked fifth. A Brexit, no doubt, would deal a severe blow to the global economy, starting from the initial impact on the U.K.’s neighboring countries including the Netherlands and Belgium.

Britain is a large export destination of many European countries. As the country will inevitably face a deep slowdown for a certain period after an EU exit, a domino effect is inevitable for the rest of Europe.

The EU, including Britain, takes up more than 10 percent of Korea’s exports.

Korea’s exports to the U.K. would no longer benefit from the tariff exemptions in its Free Trade Agreement with the EU.

Its departure from the EU means that the trade deals done under the umbrella of EU will have to be adjusted as well, together with new stand-alone deals with the U.K. A series of complex legal issues and re-adjustments of existing treaties and agreements will become inevitable.

As its departure would certainly deliver an especially powerful blow to Korea, policymakers including the Finance Ministry should closely look into the U.K. referendum and map out contingency plans to prepare for the worst.

Few factors at home and abroad are positive for the Korean economy. Korea’s industrial prowess, built on manufacturing and heavy industries, has been declining rapidly. Cases in point are the shipbuilding and shipping sectors, which have fallen from the once proud engines of Korea’s export-driven economy to sources of woe.

Some local policymakers argue that the extended slowdown in the global economy is partly to blame for the decline of the industries that once buttressed the Korean economy. But it is not a coincidence that the Korean economy has been stuck in a low-growth trap, as its traditionally strong industries like shipbuilding, steel and petrochemicals are losing their competitiveness.

A desirable way to be resilient to any external shock is to foster futuristic export industries by carrying out drastic restructuring of the economy and pouring active investment into uncharted fields.