Specialist business publisher and trade events group Informa posted flat first half pre-tax profit and said, despite economic headwinds, overall trading remains in line with company expectations for the full year.Pre-tax profit was little changed at £66.5m for the six months ended 30 June 2011 compared to £66.4m before. Revenue increased to £634.8m from £624m previously. Chief executive Peter Rigby commented, "Whilst many global growth indicators remain a concern for a sustained economic recovery, the resilience of our publishing activities and larger events underpin our confidence around our full year outlook. Furthermore, the more cyclical areas of our business are growing and we are confident would grow faster in a better economic environment."Net debt increased to £877.7m as a result of its recent acquisitions and it remains on target to end the year with a net debt to EBITDA ratio within the range of 2 to 2.5 times."We enter the second half of the year in a strong position. We will continue to seek opportunities to extend our range of tradeshows, enhance our emerging markets exposure across the entire group and add to the number of subscription based publishing products."An interim dividend of 5p has been recommended, up 11.1% from last year. CJ