Some local consumer product brands have gained significant market share in China, challenging the position of multinational companies such as Unilever NV and Procter & Gamble Co., according to research firm ACNielsen.ACNielsen said a 2002 study of more than 120 fast-moving consumer good categories showed some local products, such as shampoo and laundry detergent, have claimed spots among the top brands. It attributed the gains to local companies’ better distribution networks, effectiv...