“You look at high debt ratios and high house prices in the Nordic area and people say ‘well, that’s different from high house prices elsewhere,’” Krugman said. “It’s a warning phrase. When you hear that, you should get very worried.”

Officials are already looking at ways to limit borrowing. Looking ahead, these countries could see growth slow as they go through a deleveraging process.

Investors who would like to track the Nordic countries can take a look at the Global X FTSE Nordic Region ETF (NYSEArca: GXF). which follows companies from Norway, Sweden, Denmark and Finland. [10 Best Global ETFs of 2013]

There are also ETFs that track the individual countries, including iShares MSCI Norway Cppd Investable Mkt (NYSEArca: ENOR), Global X Norway 30 ETF (NYSEArca: NORW), iShares MSCI Sweden ETF (NYSEArca: EWD), iShares MSCI Denmark Capped ETF (NYSEArca: EDEN) and iShares MSCI Finland Capped ETF (NYSEArca: EFNL). [Demographics Weigh on Finland Economy, ETF]

For more information on Europe, visit our Europe category.

Max Chen contributed to this article.