Number of pages Google indexes from my site is gradually dropping

[TheRedPenOfDoom]

my site indexing is gradually dropping in google. in past 4 months it has dropped from 1500 to 1000.

what could be possible reasons?

what steps can i take to increase my indexing considering that i do not want to buy links ?

[incrediBILL]

Are you talking pages actually indexed or crawled?

Assuming you meant index, are all of those pages unique? They may be dropping index pages of blogs vs. the actual page, etc.

If you're talking crawling, if those pages don't update frequently there's no need to index them all the time.

Also, double check and make sure Google can actually crawl and index those pages via GWT

[Clay_More]

The greatest probability is a lack of incoming quality citations. What some might call inbound links. Wasn't this previously covered?