The healthy properties in an olive increase until the olive is half ripe and still green. As the olive ripens and matures, these benefits leave and the oil content increases. The taste becomes milder and milder because the taste of the departing benefits is bitter (antioxidants) and peppery (anti-inflammatories).
The polphenol count on a lab report is a very good indication of the level of health benefits in extra virgin olive oil.
An explanation of the powerful Anti-Inflammatory benefits of Olive Oil...oleocanthal
Antioxidants (Polyphenols) as explained by Agbiolab (a company that works for the olive industry in California) http://www.agbiolab.com/files/agbiolab_Polyphenols.pdf