three lost relations

[ShellingFord221]

Hi,
There are 56 relations in sentences, but 53 in train.txt. However, I find that three lost relations are not rare:
/business/company/industry: 6 sentences
/people/ethnicity/includes_groups: 7 sentences
/people/ethnicity/people: 169 sentences

As a contrast, there are 4 relations whose sentences are only 1. They are:
/location/fr_region/capital
/business/shopping_center/owner
/business/shopping_center_owner/shopping_centers_owned
/location/mx_state/capital

So why do you delete frequent relations and leave relations which only have 1 sentences?