Deteriorating global economic prospects continued to weigh on the Toronto stock market Wednesday as a weak outlook from resource giant Alcoa Inc. added to a pessimistic assessment from the International Monetary Fund.The S&P/TSX composite index fell for a third session, down 23.63 points to 12,249.93 while the TSX Venture Exchange dropped 13.62 points to 1,314.19.The Canadian dollar was off 0.01 of a cent to 102.18 cents US.New York indexes were also negative after Alcoa predicted aluminum demand would grow six per cent this year, down from seven per cent in the previous quarter, primarily because of slower growth in China.The aluminum producer is viewed as a broad economic bellwether as its products are used in a wide variety of industries, from vehicles to appliances.Alcoa shares were down 3.6 per cent as the company kicked off the start of the third-quarter reporting season by posting a loss of US$143 million, largely on one-time charges, while adjusted results beat estimates. Revenue of $5.83 billion also beat expectations.The Dow Jones industrials was 54.23 points lower at 13,419.3. The Nasdaq shed 1.57 points at 3,063.45, and the S&P 500 index edged down 2.21 points to 1,439.27.The International Monetary Fund on Tuesday reduced its growth forecast for the world economy to 3.3 per cent this year from its previous estimate of 3.5 per cent. The IMF forecast for growth in 2013 is 3.6 per cent, down from 3.9 per cent three months ago and 4.1 per cent in April. The IMF also reiterated its concerns over the crisis in the eurozone and warned that the recession in Spain was worse than it thought.Expectations for third-quarter earnings have been ratcheted lower because of global growth concerns. Analysts expect earnings for Standard & Poor’s 500 companies to be lower than a year ago, the first time that has happened in almost three years.“However, when you look at it from a glass half-full standpoint, the bar has been set really low,” said Allan Small, senior adviser at DWM Securities Inc. “And that could lend itself to some beating of expectations.”Small added that he’s looking ahead to Friday when the big banks start to report in order to get more clarity on earnings.“Corporate earnings really don’t start until Friday when JPMorgan Chase and Wells Fargo report and that’s going to be the first indicator of the health of the U.S. banking sector, which is a huge factor in the stock market and the emotions of investors in the U.S. and that gets carried around the world,” he said.On the Canadian earnings front, pharmacy chain franchisor Jean Coutu Group (TSX:PJC.A) said Wednesday that its quarterly net profit was $51.2 million or 23 cents per share. That compared with $66.4 million or 20 cents per share in the comparable year-earlier period when it recorded an unusual gain on the sale of U.S. assets. Revenue for its fiscal 2013 second quarter rose to $658.7 million from $635.2 million in the same fiscal 2012 period and the Quebec-based company’s shares were up five cents to $14.58.The financials sector led decliners, down 0.45 per cent as Scotiabank (TSX:BNS) shed 41 cents to $53.37.The base metals was also down 0.45 per cent as the IMF also downgraded growth prospects for China while December copper was unchanged at US$3.72 a pound. Taseko Mines (TSX:TKO) gave back seven cents to C$3.05.The energy sector also declined, down 0.37 per cent in the face of prices that continued to find support from worries that the fighting in Syria could impact Mideast oil supplies.The November crude contract on the New York Mercantile Exchange gained $1.16 to US$93.55 a barrel, adding to a gain of more than $3 Tuesday, even as the Organization of the Petroleum Exporting Countries lowered its forecast for global oil demand in 2012. OPEC said that world oil demand will grow by 800,000 barrels a day in 2012, down 100,000 barrels from its previous forecast. Cenovus Energy (TSX:CVE) fell 30 cents to C$33.90.Tech stocks also weighed on the TSX with Research In Motion Ltd. (TSX:RIM) down another seven cents to $7.55. RIM stock fell 5.5 per cent Tuesday after Jeffries and Co. analyst Peter Misek published a note saying he believes it is “more likely” that RIM won’t roll out its new phones until the end of the calendar first quarter. Investors had been hoping for a January launch.The gold sector limited TSX losses, rising 0.9 per cent as December gold declined 60 cents to US$1,764.40 an ounce. Kinross Gold Corp. (TSX:K) gained 13 cents to C$10.31.European bourses were lower with London’s FTSE 100 index off 0.34 per cent, Frankfurt’s DAX down 0.26 per cent and the Paris CAC 40 down 0.39 per cent.Traders also took in news that Britain’s BAE Systems PLC is abandoning a proposed merger with European counterpart EADS NV that would have created a global defence and aerospace giant. The deal had faced political objections from the governments of the U.K., France and Germany.In other corporate news, Bauer Performance Sports Ltd. (TSX:BAU) is buying team uniform maker Inaria International for $7 million. The hockey and lacrosse equipment company said the deal will help expand its business to include uniforms and its shares were down 24 cents to $10.71.