ESXi level 2 performance statistics

data receive rate average(host)

data transmit rate average(host)

I am finding that although these stats are listed as level 2, the ESXi hosts are not recording them in the database. They come up blank on 1 day of data. The stats are shown for real time. Other level 2 stats seem to be working e.g datastore\latency(host), data receive rate and transmit rate(VM), virtual disk\read latency(VM)