A method of producing low-viscosity water-based water-soluble polymer dispersions having a high concentration of the principal substance is achieved by polymerizing the following monomer components, (a1) 50-99.999 wt. % of at least one water-soluble monomer; (a2) 0.001-1 wt. % of at least one crosslinking monomer with at least two ethylenically unsaturated radically polymerizable groups; (a3) 0-30 wt. %, particularly 1-25 wt. %, of at least one hydrophobic monomer; and (a4) 0-25 wt. %, particularly 0.1-15 wt. %, of at least one amphiphilic monomer, in aqueous solution, in the presence of at least one polymer dispersant, to form a polymer (A), where the sum of the amounts of the components represented by the monomers (a1), (a2), (a3), and (a4) is 100 wt. % of the monomers, the weight average molecular weight of the resulting polymer (A) is at least 500,000 Dalton, and polymer (A) is incompatible with the dispersant.