The Collaborative International Dictionary of English v.0.48:

Undervaluation \Un`der*val`u*a"tion\, n.
   The act of undervaluing; a rate or value not equal to the
   real worth.
   [1913 Webster]

WordNet (r) 3.0 (2006):

undervaluation
    n 1: too low a value or price assigned to something