Turnover in Presence

[S_watzel]

Hello,

I have four years of presence-absence data for birds, with a total of 16 visits (4 visits per year), and I would like estimate the rate of change in the proportion of occupied points. In Presence, I can do this using persistence (with historical detection reversed to estimate turnover), right? But what does the rate mean? Total proportion of occupied points in years 2, 3 and 4 which were not occupied in year 1? I.e. is it an overall turnover rate meaning that e.g. if phi = 0.4 then 40% of all points experimented change in occupation status (presence or absence), or still, that 40% of only the occupied points were not occupied previously, across the 4 years?

Thank you!
Stephany