Disclosed are compositions which include an ethylene polymer derived from at least one polar monomer with one or more ester groups, which polymerize with ethylene, (e.g., a copolymer derived from ethylene and vinyl acetate or a copolymer derived from ethylene and n-butyl acrylate) and a rosin ester. The rosin ester can have a low hydroxyl number (e.g., a hydroxyl number six or five or less), a low acid number (e.g., an acid number of ten or less), a low PAN number (e.g., a PAN number of eight or less), or combinations thereof. The compositions can exhibit improved viscosity stability and/or color stability and/or a decreased amount of char particle formation upon thermal aging.