Golden visas attracted wealthy Americans to Southern Europe. Then their housing crisis followed.

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• Southern European economies have had remarkable recoveries since the financial crisis over a decade ago.
• But a surge in real estate investment, partly due to "golden visas", has led to skyrocketing housing costs.
• Northern Europe is also facing a housing crunch, despite very different economic conditions.

Southern European economies — from Greece to Portugal — have made remarkable recoveries since...