Investors honed in on Scotland last year on fears that a possible exit from the United Kingdom could disrupt the global economy. Those same eyes turned more recently to Spain after a vote in Catalonia gave separatist parties a majority of regional parliamentary seats.
Many in the northeastern region of Spain have sought political independence, but the Sept. 27 vote appears to have halted the movement temporarily: The popular vote — and therefore, the political "mandate" — for the secessionist parties came in at only about 48 percent, and the national government in Madrid is resolutely opposed to separation. Southern European bond yields hit five-month lows on Monday as investors have taken the recent national elections in Portugal and Spain as signals of growing stability in the region.
Still, pro-independence sentiment remains strong in Catalonia, which has its own language and still remembers brutal oppression under former Spanish dictator Francisco Franco. And if Catalonia were to declare independence, it would take a major portion of Spain's economic power with it.
In a research note following the vote, JPMorgan predicted that the "conflict between Catalonia and the central government will not lose intensity. ... In our view, a material offer to reframe the role of Catalonia within the national state ... is needed to soften the rising radicalism in the pro-secession camp and restore the premises for a more constructive approach."
Catalonia's 2013 regional product was 203.62 billion euros ($228 billion), according to the Public Diplomacy Council of Catalonia — about 20 percent of Spain's 2013 GDP of $1.04 trillion euros ($1.17 trillion).
Scotland, meanwhile, accounted for less than 8 percent of the U.K.'s total 2013 GDP, according to the European Commission. Scotland had slightly more than 8 percent of the U.K. population in 2012.
Despite only accounting for about 16 percent of the Spanish population, Catalonia represents about 25 percent of all Spanish exports, and it accounted for 23 percent of all Spanish industry, according to the regional government. The economy in Catalonia is relatively diversified, although about half of employment comes from manufacturing or market-related production services jobs, according to figures from the Organisation for Economic Co-operation and Development.
The effect of a Catalonian exit on Spain varies largely by how much debt it would take with it, said Xavier Sala-i-Martin, the Catalonian-born chief economic adviser for the World Economic Forum's Center for Global Competitiveness and Performance.
If Madrid were to bargain for an independent Catalonia to take 19 percent of its debt — the same proportion the region had been contributing to GDP — then the effect would largely be a wash for Spain's macroeconomic position. Catalonia has not historically grown so much faster than other parts of the country that its exit would damage future expectations of economic expansion, Sala-i-Martin said.
But if the debt reallocation were to match the 16 percent population figure, or the 11 percent current national expenditure on the region, then Spain's debt-to-GDP ratio could approach unsustainability. It's just under 100 percent now, and some already question how Madrid will be able to meet its payments if rates were to rise (an expected global outcome if the Federal Reserve moves to tighten in the U.S.).
Even worse for Spain would be if the national government works to actively oppose a Catalonia that declares independence and therefore refuses to reach a debt transfer agreement, Sala-i-Martin said. If that were the case, then its debt-to-GDP ration would balloon to something approaching 125 percent, he said.
"With the richest region gone and with almost unsustainable debt, then Spain is in big trouble," the economist said.
— CNBC's Seema Mody contributed to this report.