LONDON – The eurozone’s ability to grow its way out of the debt crisis faces a roadblock — an aging population.

While Italian Prime Minister Mario Monti and his Spanish and French counterparts push for measures to spur an economic expansion, Italy’s structural dependency ratio exceeds 50 percent.

In other words, the number of working-age people is less than half the total population. The government forecasts the ratio will reach 63 percent in 2030 and 83 percent by 2065.

Aging and shrinking labor pools are adding to budget problems in a region where the unemployment rate is already at a record high.

The risk is that without an overhaul of benefit programs, governments will be unable to balance their books as tax revenue shrinks and unfunded pension and health-care liabilities balloon. Longer-maturity bonds in Spain, Portugal and Greece are underperforming their shorter-dated counterparts amid concern the nations’ finances will keep deteriorating.

“You just can’t create growth out of thin air, and the demographic trend in the eurozone isn’t conducive to growth,” said Humayun Shahryar, who helps oversee $100 million as CEO at Auvest Capital Management in Nicosia, Cyprus.

“For a long time, the economic expansion in the region was fueled by low borrowing costs that came with the monetary union. That’s no longer the case, and the shrinking working-age population is a problem.”

The proportion of people older than 65 in Europe will rise to 19 percent in 2020 from 16.6 percent this year, according to projections from the U.S. Census Bureau. Only Japan’s ratio is higher, at 23.9 percent for 2012, hampering its efforts to shake off two decades of stagnation.

n In Spain, where the unemployment rate of 24.6 percent is the highest in the European Union, the government is paying about $8.81 billion a month to retirees, up from $4.7 billion in 2000. The ratio of workers paying into the system per retiree has fallen to 2.43, the lowest since 2003, Deputy Social Security Minister Tomas Burgos said last month.

The proportion of people aged 65 or older in Greece will climb to 26.7 percent in 20 years from 20.8 percent in 2012, according to Global Demographics, a Hong Kong-based research company. The figure for under 25 years will drop to 23.6 percent from 25.1 percent.

n Greece’s ratio of debt to gross domestic product will increase to 168 percent next year from 161 percent this year, the European Commission said in a report May 11.

“That doesn’t even include unfunded liabilities which could probably take it close to 800 percent of GDP,” said Stuart Thomson, who helps oversee about $115 billion as a money manager at Ignis Asset Management in Glasgow, Scotland.

“Governments try their best to ignore demographics because it’s outside their term of office, but it’s a very important factor for an investor like myself. Bond yields in troubled nations will stay elevated for a long time, and we don’t own them.”

The eurozone jobless rate rose to 11.1 percent in May, the highest since the data series began in 1995, the European Union’s statistics office said Monday.

The debt crisis and budget cuts have resulted in an economic slump that sent the region’s business confidence to the lowest in more than two years in June. Companies, including Deutsche Lufthansa, PSA Peugeot Citroen and Spanish news agency Efe, are seeking to trim jobs to meet weakening demand.

“There is a big challenge ahead, and the deteriorating economic outlook will make it harder to fix the problem,” said Pavan Wadhwa, global head of interest-rate strategy at JP-Morgan Chase & Co. in London.

The International Monetary Fund recommended June 21 that eurozone nations issue common debt, saying the crisis was at a “critical” stage.

EU President Herman Van Rompuy proposed a plan that centers on common banking supervision and deposit insurance, along with a phased move toward joint debt issuance. German Chancellor Angela Merkel remains opposed to debt sharing.

The risk is Europe’s debt problem is so structural and fundamental that these measures won’t solve it unless leaders address the demographic shift, said Auvest’s Shahryar, who prefers investing in countries with both population and productivity growth such as the United States, Australia and Canada.

“In Europe, we have come to a point where neither households nor governments can create much more debt,” he said. “Euro bonds aren’t going to make the population younger. They aren’t going to create jobs. They just allow some countries to borrow more. Europe needs to think of a new model of growth.”