There are three reasons for this:
First, obviously there was a tremendous sense of urgency for people to enroll in time for January 1st coverage. A drop-off after Christmas has long been expected, although this has been a bit fuzzy as the actual enrollment deadline bounced around, from 12/15 to 12/23, then 12/24 (for most states), then 12/27 or 12/31 for a handful, and finally as late as 01/06/14 for Oregon.
Secondly, I'm sure a lot of people who didn't absolutely need to enroll for Jan. 1 are in sort of a holding pattern while they wait to see how the exchange-purchased plans work out in real life. There's a big difference between being told that you'll have coverage starting on a certain date and actually hitting that date and beyond, as this article out from the L.A. Times demonstrates. In many ways, I suspect this is sort of like the early November Healthcare.gov situation, where people were watching & waiting before dipping their toes onto the website after all the technical issues they had heard about (or experienced) in the chaotic days of October.
However, the third reason is a simple one: I haven't found any new reliable numbers out of California since 12/23 or New York since 12/30. Texas, Florida, Illinois, Pennsylvania, Ohio, Georgia, Michigan, N. Carolina, New Jersey and Virginia are all run via the Federal Exchange. Since HHS itself hasn't released the HC.gov data since 11/30, that means the largest-population state that I have data for is #13, Washington...which was updated 3 days ago.
After that, the next-largest state running it's own exchange is Massachusetts (an utter mess), followed by Maryland..at #19. At this point we're into states with less than 6 million people each, which means that enrollment increases which are impressive on a state level are only making a small dent in the overall national numbers. In other words, it's not that the number of enrollments have necessarily dropped off that much, it's just that the states representing about 85% of the country have been maintaining radio silence for a couple of weeks now.
Now for the good news: New York should be releasing their latest tally at any time. California should be just about done sorting out the deluge of last-minute partially-completed enrollments that they've been sorting through for the past 2 weeks. Most of all, the official HHS Dept. report for December should (based on the release dates of the October and November reports) be released sometime today or over the weekend.
The official HHS report should finally answer the question of just how full of beans my own numbers have been over the past crazy month. And perhaps we'll finally find out what the hell is going on in the District of Columbia (HHS had no official data for them through November!) and Hawaii (they had a small number for private enrollments but zilch for Medicaid expansion).
Anyway, I've also tweaked the spreadsheet itself a bit more; I've added 2 new columns which show the states that 1) have agreed to Medicaid Expansion and 2) have agreed to allow their insurance companies to extend the old, non-ACA compliant plans by 1 year. Note that even if the state allows this it doesn't necessarily mean that all of the companies in that state are doing so; some are, some aren't, some are only extending plans by 3 months and so on. Messy.
ArcticStones and I ae also working on a separate issue which I hope to have news on soon...but until then, everyone will have to sit tight.