Macquarie Group shares closed at a two-year low yesterday, following reports of a Citigroup note on the company that had downgraded it to a sell. Citi's analysis slashed the target price on the stock from A$38 to $30.50. The stock fell almost three per cent yesterday, to close to $32.Citi cited Macquarie's weak market share in mergers' and acquisitions' advisory work, lower earnings from its securities' business and the high cost of its expansion into overseas markets.The strong appreciation of the Australian dollar over the past year has cut into Macquarie's overseas earnings.Citi's view is that Macquarie's current return on equity is lower than its cost of capital.