TORONTO - The Ontario Teachers' Pension Plan says it earned a 14.3 per cent return last year.

The money manager said it earned $13.3 billion in investment income in 2010 -- ending the year with $107.5 billion in net assets.

But it faces "serious funding challenges," including a $17.2-billion preliminary funding shortfall due to longer retirement periods and low real interest rates.

The fund now pays out $1.8 billion more each year than it receives in contributions.

The plan's sponsors, the Ontario Teachers' Federation and the Ontario government, are studying how to eliminate the preliminary shortfall, which must be eliminated in 2012.

The fund changed its asset mix last year, adjusting some targets and reclassifying some assets, including the sale of its stake in Maple Leaf Foods (TSX:MFI).

"Our investment team remained true to our investment fundamentals, taking appropriate risks to earn solid returns, while seeking the best diversification to meet our plan's long-term needs," Teachers' president and CEO Jim Leech said in a statement.

The Ontario Teachers' Pension Plan administers the pensions of 295,000 active and retired teachers in the province.

Some of its major assets include mall landlord Cadillac Fairview, and Maple Leaf Sports and Entertainment, the company that owns the Toronto Maple Leafs and Raptors.