Will a drop in indexed pages significantly affect Google rankings?

[rdreich49]

I am doing some research into why we were bumped from Google's first page into the 3rd, fourth and fifth pages in June of 2010.  I always suspected Caffeine, but I just came across some data that indicates a drop in indexed pages from 510 in January of that year to 133 by June.  I'm not sure what happened but I believe our blog pages were de-indexed somehow.

What I want to know is could that significant drop in indexed pages have had an effect on our rankings at that time?  We are back up to over 500 indexed pages, but have not fully recovered our first page positions.

[AlanMosley]

It could , but not always.
it depends on your linking structure, if your linking was pushing page rank from those pages to your ranking page then yes.

this page explains it all
http://www.webworkshop.net/pagerank.html

[rdreich49]

Thanks for your answer and reference, Alan.  As many of our internal pages link to the home page, any juice the lost pages may have been passing to it may have been lost, correct?  I'm pretty sure it was our blog pages that weren't indexed during that period and many of them had some good links to them.

[AlanMosley]

Yes, general a blog would link back to the home page and not every page, os yes i would say they lost you some rank.