Today’s Supplemental Results Index is where Google places the majority of Web content — most of which is unique. Documents only reach the Main Web Index after Google finds enough value-passing links pointing to them. The number of links varies because of their internal PageRank (Google does not publish internal PageRank and the Toolbar PR values are worthless for determining whether links pass value).

Duplicate content MAY land in the Supplemental Results Index simply because there are too few links pointing to it, but telling Google not to index your date archive pages won’t increase the number of links pointing to your posts or blog.

Also, there are no reliable queries that show you which of your pages are in the Supplemental Results Index. Nor was the query that people were using in 2007 ever a reliable test (the query had people performing a site search and subtracting out garbage).

Generally speaking, a page in the Supplemental Results Index will not:

1) Pass link anchor text to other pages
2) Be cached very often
3) Be found for unique expression queries (unless the queries use rare words)
4) Be shown first if they are the most relevant pages for a given query

Google has mislead people about the impact that being in the Supplemental Results Index has on their search visibility. Unfortunately for searchers and Web publishers alike, any page that is in the Supplemental Results Index will be shown AFTER less relevant pages in the Main Web Index.

It doesn’t matter what you do with your blog software — that won’t change the way Google currently works.