pg_autovacuum / pg_class

Hello,

I have a simple question about auto-vacuuming. We are running a Postgres
8.1 and I've noticed that some of the tables are not analyzed by the
pg_autovacuum daemon. That is - when I select the rows from pg_class,
all the important values (relpages, reltuples) are 0.

I've noticed this in case of newly created tables (that is not older
than 1 month). My 'theory' is this - the table has to be analyzed by
hand at the beginning, otherwise the pg_autovacuum won't process it. Am
I right?

We use default values for all pg_autovacuum related parameters in
postgresql.conf, and there are no rows in pg_autovacuum. The new tables
are growing pretty fast (about 1.000.000 of rows each month), so the
thresholds should be exceeded pretty very fast.

But maybe this is caused by some stupid misconfiguration and/or is a
known feature ...

thanks for all your advices
Tomas