Post-Brexit Britain arrives

• Yes, but: Northern Ireland is still part of the U.K., while trading as though it is part of Europe. That means anybody moving goods between Northern Ireland and Great Britain needs to fill out a customs declaration first.
• An analogy: Imagine businesses in Alaska being able to trade freely with Canada and Mexico, but needing to fill out paperwork in order to import or export anything to the rest of the USA.
• Gibraltar, similarly, will join the Schengen Area. That means Europeans will be able to travel in and out freely, while visitors from the U.K. are forced to show their passports at a border control.

The trade deal with Europe puts zero tariffs on goods. Most of Britain's economy is in the services sector, however — which aren't covered at all in the deal. (The U.K.'s businesses have had just one week to prepare for the new trade regime, which was agreed to on Christmas Eve.)

• Britain exports about $35 billion of financial services to the EU every year, and another $134 billion of other services, including legal, accounting, advertising, architecture, insurance, tech support, and much more.
• As for the U.K.'s trade relations with the rest of the world, 62 trade agreements have been signed — although many big ones, including the U.S., China and India, are still up in limbo.

By the numbers: The U.K. Office for Budget Responsibility estimates that Brexit will leave the country about 4% poorer than it would have been as part of the EU.

• That's just the economic cost. The cultural costs associated with the end of free movement of labor between Britain and the continent are less quantifiable, but arguably larger.

• Both Europe and the U.K. may also be less secure, now that British police no longer have access to the Schengen Information System. Last year, they queried Europe's largest security database more than 1.6 million times per day.

The future of the U.K. is also now at risk.

• Scotland wants to secede and become an independent European nation.
• Northern Ireland might vote to leave the U.K. and join Ireland, reuniting the island.

The other side: "For the first time since 1973 we will be an independent coastal state with full control of our waters," said U.K. Prime Minister Boris Johnson, announcing the deal.

The bottom line: For the past 40 years, Britain found peace and prosperity as one of the most important players in a community of more than 400 million people. As of today, it has become, once again, an island off the coast of Europe.