It might still be the world's biggest steelmaker, but for investors ArcelorMittal is a shadow of its former self. After losing about $100-billion in market value, the supplier of steel for New York's One World Trade Centre and London's Wembley Stadium is worth the same as the operator of Legoland theme parks, which makes replicas of these iconic buildings.For that, blame China.Demand from the biggest steel consumer is set to fall this year and beyond as the government shifts the economy away from manufacturing. That has led local mills to export excess steel cheaply, collapsing world prices and profits.Yet the steelmaker in many ways remains a giant. Sales in 2014 were $80-billion - up with global giants Vodafone and Unilever.ArcelorMittal still employs 222000 people. Production of 93 million metric tons of steel in 2014 was greater than the output of the US or India. If it was a country, it would be the third-largest steelmaker, trailing China and Japan.But it just isn't big enough to cope with the flood of Chinese steel now hitting the market. ..