The Collaborative International Dictionary of English v.0.48:

Productivity \Pro`duc*tiv"i*ty\, n.
   The quality or state of being productive; productiveness.
   --Emerson.
   [1913 Webster]

         Not indeed as the product, but as the producing power,
         the productivity.                        --Coleridge.
   [1913 Webster]

WordNet (r) 3.0 (2006):

productivity
    n 1: the quality of being productive or having the power to
         produce [syn: productiveness, productivity] [ant:
         unproductiveness]
    2: (economics) the ratio of the quantity and quality of units
       produced to the labor per unit of time

Moby Thesaurus II by Grady Ward, 1.0:

131 Moby Thesaurus words for "productivity":
   abundance, amperage, amplitude, armipotence, authority, beef,
   black power, bountifulness, brute force, charge, charisma,
   cloud of words, clout, cogence, cogency, compulsion, copiousness,
   creativeness, creativity, diffuseness, diffusion, diffusiveness,
   dint, drive, duress, effect, effectiveness, effectuality, effusion,
   effusiveness, energy, extravagance, exuberance, fecundity,
   fertile mind, fertility, flower power, fluency, force,
   force majeure, forcefulness, formlessness, fructiferousness,
   fruitfulness, full blast, full force, generousness, gush, gushing,
   influence, ingenuity, invention, inventiveness, logorrhea,
   lushness, luxuriance, macrology, main force, main strength, mana,
   might, might and main, mightiness, moxie, muscle power,
   originality, outpour, overflow, palilogy, pizzazz, plenteousness,
   plentifulness, pleonasm, poop, potence, potency, potentiality,
   power, power pack, power structure, power struggle, powerfulness,
   pregnancy, pregnant imagination, prepotency, procreativeness,
   prodigality, productive capacity, productiveness, profuseness,
   profusion, prolificacy, prolificity, puissance, pull, punch, push,
   rampancy, rankness, redundancy, reiteration, reiterativeness,
   repetition for effect, repetitiveness, richness, sinew, steam,
   strength, strong arm, superabundance, superfluity, superflux,
   superiority, superpower, swarmingness, talkativeness, tautology,
   teeming imagination, teeming womb, teemingness, tirade, validity,
   vehemence, vigor, vim, virility, virtue, virulence, vitality,
   wattage, weight