(The Wall Street Journal) -- The sub-prime mortgage crisis has been a financial catastrophe for much of Wall Street. At Goldman Sachs, thanks to a tiny group of traders, it has generated one of the biggest windfalls the securities industry has seen in years.

The group's big bet that securities backed by risky home loans would fall in value generated nearly $4bn (€2.8bn) of profits during the year ended November 30, according to people familiar with the firm's finances. Those gains erased $1.5bn to $2bn of mortgage-related losses elsewhere in the firm. On Tuesday, despite a terrible November and some of the worst market conditions in decades, analysts expect Goldman to report record net annual income of more than $11bn.