Hello Daniel.

On 9 September 2011 14:32, Daniel Kinzler <daniel@brightbyte.de> wrote:
Apparently, we are approaching 20 Million pages worldwide (by some count. I have
no idea what that actually includes).
(...) 
I'm aware that this number can never be accurate, and there are several valid
definitions of "page", etc. I'm just looking for something that is "close
enough" to show off.

I think the 20 million is based on Special:Statistics[1], which shows 'Content pages' (currently 3.7M on enwiki). This is the 'ss_good_articles' column in the site_stats table:

mysql> select ss_good_articles from site_stats;
+------------------+
| ss_good_articles |
+------------------+
|          3733749 |
+------------------+
1 row in set (0.00 sec)

It might actually be interesting to solve this in a more global way: a site_stats toolserver table that incorporates all site_stats values for all wikis.

Of course, for the nice counter, you could want some more data, such as the increase per unit of time, so you could use javascript to 'automatically' update the counter.

Best,
Merlijn