:-) Here's the story and happy ending... The note under the "Index Status" chart related to the Webmaster Tools update reads: **Update: As of 3/9/14, Index Status data precisely reflects the specific URL variant for your verified site (e.g., http://www.example.com data is distinct from https://example.com)**
. The site I was working on had the exact same drop in its Index Status as +Jodi Bennett shared. We believed it's because Google had non-www and www results as part of the Index Status before, but post 3/9, the data for non-www and www became separated. So, here's what we did: 1. We validated both non-www and www in the Webmaster Tools accounts. 2. In the "Site Settings" for each domain we set the preferred domain for Google to display (in their case it was the non-www). 3. We made sure there were no robots.txt errors for the website preventing a complete crawl. 4. We added the canonical tag to their pages. Especially their homepage. We believe the canonical tag is what made the difference. Seven days later the "Index Status" for their Webmaster Tools profiles improved and has been on the rise ever since. This makes sense given what Google has stated the WMT update did: "reflects the specific URL variant..." ... My recommendation to all webmasters out there: make sure Google understands, as best as you can tell it, which domain is the one you prefer it shows in the search results. And claim both the non-www and www in Webmaster Tools because in that big Mountain View box, after 3/9, the URL data in the index is reported differently for non-www and www. Please let me know if you try this and it works. I'd love to get more qualified tests from others to share with clients.