Did you know that different extraction methods mean not only different chemical composition, but also different yields?
Here is a comparison of steam distillation and supercritical CO2 extraction of some plant materials.
While the differences are not so dramatic for some, such as clove bud, they are quite significant for others. Rosemary CO2 extraction results in 10 times the yield of steam distillation, for example.
The reason is that carbon dioxide extracts a wider range of molecules than does steam.
(Data from Mukhopadadhyay, M., Natural Extracts Using Supercritical Carbon Dioxide, CRC Press, 2000. ISBN 0-84930819-4)