The Haumea family is currently the only identified collisional family in the Kuiper belt .
We numerically simulate the long-term dynamical evolution of the family to estimate a lower limit of the family ’ s age and to assess how the population of the family and its dynamical clustering are preserved over Gyr timescales .
We find that the family is not younger than 100 Myr , and its age is at least 1 Gyr with 95 % confidence .
We find that for initial velocity dispersions of 50 - 400 ms ^ { -1 } , approximately 20 - 45 % of the family members are lost to close encounters with Neptune after 3.5 Gyr of orbital evolution .
We apply these loss rates to two proposed models for the formation of the Haumea family , a graze-and-merge type collision between two similarly sized , differentiated KBOs or the collisional disruption of a satellite orbiting Haumea .
For the graze-and-merge collision model , we calculate that > 85 \% of the expected mass in surviving family members within 150 ms ^ { -1 } of the collision has been identified , but that one to two times the mass of the known family members remains to be identified at larger velocities .
For the satellite-break-up model , we estimate that the currently identified family members account for \sim 50 \% of the expected mass of the family .
Taking observational incompleteness into account , the observed number of Haumea family members is consistent with either formation scenario at the 1 \sigma level , however both models predict more objects at larger relative velocities ( > 150 ms ^ { -1 } ) than have been identified .