The present invention relates to a composition comprising an aqueous dispersion of multistage polymer particles comprising a first and a second phase, wherein the first phase comprises structural units of a carboxylic acid monomer or a salt thereof, and a nonionic ethylenically unsaturated monomer; and wherein the second phase comprises a first and second polymer, wherein the first phase or the second phase first polymer or both comprise structural units of a high Tg hydrophobic monomer; and wherein the second phase second polymer comprises at least 80 percent structural units of styrene. The high Tg hydrophobic monomer is defined as being one or more of the following monomers: cyclohexyl methacrylate, isobornyl methacrylate, 4-t-butyl methacrylate, t-butylstyrene, or n-butyl methacrylate. The multistage polymer particles are useful as opaque polymers, which are used in pigmented coating formulations to reduce the load of TiO2. The particles exhibit excellent collapse resistance and unusually low dry bulk density, and do not require acrylonitrile to achieve this desired combination of properties.