In the graphic accompanying yesterday's front page report 'Pollution study points to dangers of 'canyon effect' ' two of the figures were erroneously transposed. The count of ultrafine particles outside the old Hang Seng Bank building was 79,208, while the reading at Statue Square was 45,193.

In the Insight article 'Heads above water' published yesterday on page A11, we incorrectly stated: 'In its latest forecast, the International Monetary Fund expects gross domestic product in advanced economies to grow by just 0.5 per cent this year compared with 2.6 per cent in 2007.' It should have been: 'The IMF expects output in advanced economies to shrink by 2 per cent this year, the first contraction in more than 60 years.' We apologise for the error, which was introduced during the editing process.