Nielsen, the global market research company, is reportedly about to start the search for bankers in the US to handle a $21bn (£13.5bn) IPO. The floatation by the group, which last year took an equity stake in CGA Strategy, the Stockport-based UK on-trade specialist, is seen as a test of investor’s appetites in the US. Nielsen was taken private in a landmark €7.6bn ($10bn) buy-out in 2006 featuring six private equity firms: Alpinvest, Blackstone, Carlyle, Hellman & Friedman, Kohlberg Kravis Roberts and Thomas H Lee. These private equity firms hoped the IPO would value the company – formerly VNU – at 11 to 13 times earnings before interest, tax, depreciation and amortisation, people familiar with the plans said.