The sendmail statistics file is ordinarily installed automatically:

cp /dev/null statistics
install -c -o bin -g bin -m 444 statistics /etc/mail/statistics

There are legitimate reasons to suppress the installation of this statistics file. Consider a site that has written custom software to monitor the sendmail program's performance. Such a site might wish to eliminate the sendmail statistics file because it is redundant. To prevent installation of the statistics file, you can define this confNO_STATISTICS_INSTALL macro:

define(`confNO_STATISTICS_INSTALL')

With this line in your m4 build file, the earlier install line will be eliminated during installation.