Yea, oops, Paraic, your right, that's why I'm not a mathematician. But I got your attention, didn't I. : )
Actually, it's about 5-6% for land. It's higher for some other finite assets.
To check this use your own house. If you can rent for your house for $2000 per month and the land part of it worth $300,000, ignoring your house, and compensating for repairs and renovations, then the the annual rental value of your house would be about $1500 x 12 = $18,000. which is about 6% of land value.
Here's the best study on the amount of rent available.
Total Resource Rents of Australia from 2013, it shows that in Australia most taxes can be replaced by economic rent capture.