Remember Y2K? Banks and governments worried the date-time software conversion at the start of the millennium would blow out the global computer network.

After spending extra on upgrades - and driving survivalists to stockpile dried food and bottled water - the world moved forward, mostly unscathed.

That's about what Hank Smith, boss at $6.5-billion-asset Haverford Trust Co. expects of "Brexit," Friday's vote by English voters to leave the European Union. (Their Scottish and Northern Irish partners in the United Kingdom voted to stay, raising the prospect of a U.K. breakup.)

The vote "shocked" London investors, who had made a "seriously bad bet" that their nation would opt to remain in the EU, investment manager James Mayer of Tower Bridge Advisors in West Conshohocken told clients of Boenning & Scattergood.

The dollar rose, gold jumped, U.S. Treasuries are in demand, and the Federal Reserve has likely postponed rate cuts until at least this fall, Mayer said.

Big banks like Barclays and Lloyds traded down as much as 20 percent. U.S. banks like Citi and Morgan Stanley also plunged. Investment firms like Lincoln National and Legg Mason and regional lenders like Pittsburgh- based PNC and Vernon Hill's London-based Metro Bank also traded lower.

But that just left most share prices where they were a week ago, Haverford's Smith noted. Uncertainty feeds anxiety, but "this is a mostly political issue, not an economic issue," he told me. "This won't drag the globe into a recession."

U.K.-based drug giants GlaxoSmithKline and AstraZeneca, whose U.S. bases are in the Philadelphia area, briefly traded higher early Friday.

"They are multinational businesses with a significant degree of U.S. and [outside-] Europe revenue," noted Alan J. Cohn, partner at Sage Financial Group, West Conshohocken. As the British pound drops, their dollar profits rise. "There is also a flight to safety" from U.K. investors away from U.K. exporters and financial stocks, he added.

"The U.K. could be facing a mild recession," but "the direct impact on the U.S. economy would be minuscule" even if British companies default on loans from U.S. banks, Wells Fargo global economist Jay Bryson told clients. But indirect effects - on the future of the rest of the EU - are harder to see, he added.

"T-shirt makers will have fun with 'Brexit-Nexit' " in other European countries, said Matthew Taylor, partner at Permit Capital Advisors, West Conshohocken. He said the markets are watching the "political fallout" in the coming Spanish and French elections and possible EU referendums elsewhere. The EU faces high debt, slow growth, and other obstacles, he noted.

Mayer, in the Boenning report, says the problems feeding political and social unrest such as Brexit, America's contentious primaries, and nationalist movements in Europe, are more basic: An aging world population, which demands costly services, is contributing to slower growth and fiscal challenges that are tough to solve.

The British American Council sought to calm Philadelphia-area businesses' fears about the U.K.-EU split. "The strength of the U.K.-U.S. economic relationship over the long term and the many aspects of the U.K.'s attractiveness for foreign investors all have proven that the U.K. can provide a business-friendly environment," the council said in a statement. No matter what's next, "the trans-Atlantic economy will continue to be a source of opportunity."

"The U.K. has the world's fifth-largest economy, and the U.K. and U.S. are such massive trading partners with each other, it may not have such long-term ramifications," added past council president Howard Silverstone, director of Forensic Solutions, an investigative-accounting firm in Haddonfield.

The plunging markets "are reacting to uncertainty:" Conservative Prime Minister David Cameron's rival Labor leaders also backed the EU and are also expected to resign after voters' rejection as well as the possibility that Scotland and Northern Ireland might choose Europe over England, Silverstone told me.

"That's a lot of short-term turmoil for a small island," Silverstone concluded. But he expects the U.K. will remain America's main "gateway" to larger European markets.

JoeD@phillynews.com

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