Since Jan 26, 2015 no daily aggregations of page view dumps have been generated (and hence no monthly either for Jan)
The script stumbles over a data file that seems to be out of order, even when all data have been sorted prior to merge.
At least 3 users reported the issue in previous weeks.
http://dumps.wikimedia.org/other/pagecounts-ez/merged/2015/2015-01/