pg_stats.correlation rule of thumb for re-clustering a table?

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(By re-cluster, I of course mean pg_repack.)

Purely OLTP tables (that are only accessed randomly) can of course live with 0% correlation, but lots of tables are mixed-use, and so benefit from physical ordering on a carefully chosen field..

SELECT abs(correlation)::numeric(3,2) as correlation
FROM pg_stats
WHERE schemaname = 'foo' AND tablename = 'bar'
  AND attname = 'blarge';
 correlation
-------------
        0.84
(1 row)

Obviously 84% is no need to worry, but what about 60% or 40%? Currently, I use 60%, but would like to do better.

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