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This could be for multiple reasons. If you are looking at raw total links (not unique domains) linking to you, one blogger linking to you with a sitewide link and if that person change his blog's link display from sitewide to homepage only can impact numbers like that. Have you also been monitoring your competitor links ? How have they changed ? Also, the quality of the sites OSE uses it's in index would improve over time, in which case spam blogs etc might get dropped, thereby causing in reduction in the number of links. There could be a number of things. See OSE Stats below from their update on 9th Oct, 2014 166,012,290,869 (166 Billion) URLs 14,298,548,989 (14 Billion) subdomains 168,560,672 (168 Million) Root Domains 836,560,885,910 (836 Billion) Links Followed vs. Nofollowed 2.51% of all links found were nofollowed 63.17% of nofollowed links are internal 36.83% are external Rel Canonical - 19.74% of all pages now employ a rel=canonical tag The average page has 105.24 links on it 87.45 internal links on average 17.79 external links on average