I knew some of the responses would be defensive but on the whole, people have explained that the empty seats are mainly due to people that cannot commit to a season watching the team due to their personal circumstances or the club have allocated a few seats for staff/academy members etc and there is no interest in Cat C games etc.
In any stand of the ground, I feel there should be a minimum requirement attendance of 12 of the 19 Premier League games. If the person falls below, then an average is taken over 3 years. A Fan Fair Play type scheme if you will. If you attend less than 36 games in 3 years, your card MAY be resold. This would allow for change in personal circumstances(ie redundancy/illness etc). The Family Stand should be exempt IMO as at 16 they get turfed out anyway. The academy freebies should be reallocated to the North Stand 3rd tier.