I created a microsite for sustainable packaging and found that Google's Page Rank appears for the index page but does not appear for several of the interior pages, even after 18 months.

You can view the site at http://www.diamondpackaging.com/green. There are approximately 40 pages in the site.

Does this affect search engine ranking?

Thanks,
Wilbury

try to gather links on those inner pages.. page rank are also based on link popularity..

This is not strange, Google might not have ranked those inner pages. Build more and more links to inner pages, they will have PR automatically.

Google gives Pagerank to Quality pages. try to make it unique and gather good backlinks to inner pages. try to optimize ur inner pages and inter link them properly so as to pass PR to all pages.
its difficult to get pagerank to all inner pages but u can try to get it

Build back links for inner pages. Do all sort of SEO activities for each page on your site such as deep link directory submission, Article submission, Forum participation etc. Try to make unique Title, Keyword, Meta description for each page.......

While assigning PR Google treats each page as a separate entity and gives different PR as per the page deserve. It is not at all necessary that if you got a PR on home page the inner pages will also get it. You have to do link building for each and every page you want to have PR.

Thanks to everyone for your input.

I've made a concerted effort to create pages with content specific to a certain topic. However, I should try getting more links to the inside pages as opposed to simply pointing them to the home page.

I thought that the sheer volume of quality pages would improve the overall page rank for a site?

Maybe your pages not indexed by Google.

That's odd. Is this a new site? If it s new website, it is normal that you get a hard time dealing with it. Did you do any link building campaign for your site?

The site has been live for about 18 mos. I believe all of the pages are indexed by Google. I also included them in the Google Site Map.

Does this affect search engine ranking?

Pagerank is a result of structure traffic and content. Make sure the page is indexed and if it is then check your link structure and Juice leekage. If all is well there then change the content and add some deep links.