Maybe there's still some fight in the PostgreSQL competition, after all. [Update: Or maybe it has more to do with internal changes at MySQL - see below.] According to data compiled by MarkMail, PostgreSQL messaging traffic dwarfs that of MySQL's, suggesting that the Postgres community is more active than MySQL's:
Comparing PostgreSQL and MySQL is kind of interesting. With all the talk about the LAMP (Linux/Apache/MySQL/PHP-Perl-Python) architecture you'd think MySQL had a lock on the open source database market, but based on simple message traffic analytics, PostgreSQL has a much higher level of community involvement. Looking at January 2000 onward, the MySQL lists have amassed 340,000 messages with about 3,000 new messages each month. In the same time period, the PostgreSQL lists have hit 583,000 messages with 7,000 new each month.
I'm surprised. A (highly imperfect) Google Trends analysis shows MySQL (blue) dwarfing PostgreSQL (red) in terms of search interest (but both are on the decline):
Of course, if you do an (also very imperfect) Alexa analysis, MySQL(.com) is way above Redhat.com, postgresql.org, sugarcrm.com, and jboss.org.
Does this mean anything? Not sure. I do know that MySQL was recently bought for $1 billion and I haven't seen anyone buying up EnterpriseDB, Greenplum, and other PostgreSQL companies (though this isn't to say, by any means, that it won't happen). But clearly the messaging on community mailing lists is a very imperfect means to measure popularity.
UPDATED: I received a useful bit of information that likely explains why MySQL's messaging traffic appears to have hit its peak in 2001 to 2003, and declined since then. This almost certainly relates to MySQL moving its general and bugs discussions from the mailing lists to forums and bugs system. In other words, traffic hasn't gone down...it has just moved to different forums that MarkMail doesn't track/host.