The present invention is a process for producing low density copolymers of ethylene and alpha-olefins having from 4 to 10 carbon atoms in three polymerization stages in the presence of an olefin polymerization catalyst where a low molecular weight copolymer of ethylene is produced in two of the stages and a high molecular weight copolymer in one of the stages. The resulting copolymers have a low density of not more than 920 kg/m3.