A developer includes a carrier and a toner, wherein the toner contains toner particles of at least one binder, at least one colorant, and external additives, wherein the developer has a trimmer clogging value in relation to toner triboelectric charge and toner cohesion expressed according to the equation (-0.80+0.039.times.(% toner cohesion)+0.026.times.(toner triboelectric charge) (.mu.C/g)) of less than or equal to about 3.2.