diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml
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*** a/doc/src/sgml/ref/create_index.sgml
--- b/doc/src/sgml/ref/create_index.sgml
*************** Indexes:
*** 746,751 ****
--- 746,761 ----
    </para>
  
    <para>
+    The system collects statistics on all of a table's columns.
+    Newly-created non-expression indexes can immediately
+    use these statistics to determine an index's usefulness.
+    For new expression indexes, it is necessary to run <link
+    linkend="sql-analyze"><command>ANALYZE</command></link> or wait for
+    the <link linkend="autovacuum">autovacuum daemon</link> to analyze
+    the table to generate statistics about new expression indexes.
+   </para>
+ 
+   <para>
     For most index methods, the speed of creating an index is
     dependent on the setting of <xref linkend="guc-maintenance-work-mem"/>.
     Larger values will reduce the time needed for index creation, so long