Current self-citation rates

[Wheeler, Terrie (NIH/OD/ORS) [E]]

Group,

What is the current estimated self-citation rate?  I have found an older article that put estimated self-citation rates at 30% or above.

Seglen PO.  Citation rates and journal impact factors are not suitable for evaluation of research.  Acta Orthop Scand 1998; 69 (3): 224 - 229.

To support this, it references:

Moed HF, Burger WJM, Frankfort JG, Van Raan AFJ.
On the Measurement of Research Performance: The Use
of Bibliometric Indicators. Leiden, Science Studies Unit,
LISBON-Institute, University of Leiden; 1987:l-199.