Leaving the European Union could cost the U.K. 1 billion pounds ($1.45 billion) in lost advertising spending through 2030 because of a reduction in economic growth, media-buying agency ZenithOptimedia said.

A “leave” vote in the U.K.’s June 23 referendum would reduce gains in ad spending by 70 million pounds a year, the agency said in a report Wednesday, joining other business groups in warning of the costs of so-called Brexit. Zenith, part of Paris-based ad company Publicis Groupe SA, based its forecast on an analysis by the U.K. Treasury, which said the country’s economy in 2030 would be 6.2 percent smaller outside the EU than inside the bloc.

U.K. Advertising Spending Growth %

201620172018
With Brexit9.23.94.5
Britain Stays9.24.34.8

Source: ZenithOptimedia

Zenith said the effects of Brexit would not be felt for at least several months, based on a survey of advertisers’ intentions. Respondents said they hadn’t changed budgets and didn’t intend to do so in the event of a vote to leave. Over the longer term, spending would be held back by a reduction in product introductions stemming from slower economic growth, the agency said.

“While the immediate effect would be muted, Brexit would have a long‐term cost for the U.K ad industry,” said Jonathan Barnard, Zenith’s head of forecasting. “It would also threaten to make cross‐border accounts in Europe more costly and cumbersome to operate.”

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