Multiple adsense units per page ?

[s2kinteg916]

Do u believe that displaying multiple ad units per page decreases overall CPC ?

For example showing 1 vs showing 4 ad units

[Cutter]

No. Sometimes the lower ranked ads actually pay more per click.

[etech-martin]

I think you should visit Google support guides here
https://www.google.com/support/adsense/bin/index.py?fulldump=1
IMO,It will help you to get clear idea. ;)