  In a wide class of paired comparisons, especially in the sports games, in
which all subjects are divided into several groups, the intragroup comparisons
are dense and the intergroup comparisons are sparse. Typical examples include
the NFL regular season. Motivated by these situations, we propose group
sparsity for paired comparisons and show the consistency and asymptotical
normality of the maximum likelihood estimate in the Bradley-Terry model when
the number of parameters goes to infinity in this paper. Simulations are
carried out to illustrate the group sparsity and asymptotical results.
