In this work I investigate the redshift evolution of pair fraction of a
sample of 196 massive galaxies from z = 0 to 3, selected from the COSMOS field.
We find that on average a massive galaxy undergoes ~ 1.1 \pm 0.5 major merger
since z = 3. I will review the current limitations of using the pair fraction
as a probe for quantifying the impact of mergers on galaxy evolution. This work
is based on the paper Man et al. (2011).Comment: 4 pages; to appear on the Conference Proceedings for "Galaxy Mergers
in an Evolving Universe", held in Hualien, Taiwan (October 2011
