WONDERING how share prices will fare this year?Nouriel Roubini, the co-founder of Roubini Global Economics, told an audience in New York this week that the global economy faced the same risks that bedevilled investors last year.That means asset prices could again be tossed around by rising commodity prices, concerns about Europe, uncertainty in the Middle East, and extreme weather events.So, we could be in for a rocky ride. As Bloomberg points out, the Dow Jones Industrial Average - the benchmark index of the 30 biggest US companies - had four consecutive days of 400-point swings last year, the longest run since 1896.And since April, the average daily "price move" of the S&P 500 - another bellwether index, comprising the US's 500 biggest companies - has been 1.2 percentage points: close to twice the 50-year average before the Lehman Brothers collapse in 2008.The Australian sharemarket takes a lead from those indexes.Meanwhile, the head of international economics at NAB, Tom Taylor, explained why the World Bank's forecast for global growth, revised downwards this week from 3.6 per cent to 2.5 per cent, sounded worse than it ought.As Taylor wrote in a note to clients, NAB thinks global growth will be 3.25 per cent in 2012, similar to other private sector forecasters. And when measured the same way, the World Bank's forecast is actually 3.4 per cent - greater than NAB's."The difference is largely illusory and reflects how forecasts are compiled," Taylor wrote. "And, for those of you who heard the headline that the International Monetary Fund was forecasting a much worse downturn than during the global financial crisis, that was their negative case scenario, not their central forecast."For the week, the local sharemarket finished slightly higher, up 1.05 per cent on last Friday's close, after relatively positive news from Europe's bond auctions.Yesterday, the benchmark S&P/ASX200 edged up 24.8 points, to 4239.6. The broader All Ordinaries rose 24.4 points, to 4303.Energy and materials stocks performed well. Iluka Resources gained $1.33 to $18.16. Woodside Petroleum rose 51? to $33.99.Meanwhile, the consumer staples sector lost ground, dragged down by Woolworths and Wesfarmers. Woolworths dropped 23? to $24.90. Wesfarmers lost 13? to $30.24. "The broad tone of the market has been supportive this week," a CMC Markets analyst, Ric Spooner, said.