An aqueous dispersion of a copolymer with copolymerized units a) of at least one ethylenically unsaturated carboxylic acid, b) of at least one nonionic ethylenically unsaturated surfactant monomer, c) of at least one C1-C2-alkyl methacrylate, d) of at least one C2-C4-alkyl acrylate, where the alkyl chain length averaged over the number of alkyl groups of the alkyl acrylate is 2.1 to 4.0, is described. Following neutralization with alkali, the dispersion serves as associative thickener, in particular for liquid detergent and cleaner formulations. The thickeners are characterized by high transparency and high thickening effect coupled with high shear dilution.