diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 7befc63860..6cad079132 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7342,7 +7342,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         Specifies a fraction of the table size to add to
         <varname>autovacuum_vacuum_insert_threshold</varname>
         when deciding whether to trigger a <command>VACUUM</command>.
-        The default is 0.0, which means that the table size has no effect.
+        The default is 0.01 (1% of table size).
         This parameter can only be set in the <filename>postgresql.conf</filename>
         file or on the server command line;
         but the setting can be overridden for individual tables by
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index dbf418c62a..904fbffd94 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -777,20 +777,28 @@ vacuum threshold = vacuum base threshold + vacuum scale factor * number of tuple
     <xref linkend="guc-autovacuum-vacuum-scale-factor"/>,
     and the number of tuples is
     <structname>pg_class</structname>.<structfield>reltuples</structfield>.
-    The number of obsolete tuples is obtained from the statistics
-    collector; it is a semi-accurate count updated by each
-    <command>UPDATE</command> and <command>DELETE</command> operation.  (It
-    is only semi-accurate because some information might be lost under heavy
-    load.)  If the <structfield>relfrozenxid</structfield> value of the table is more
+    The table is also vacuumed if the number of tuples inserted since the last
+    vacuum have exceeded the defined insert threshold, which is defined as:
+<programlisting>
+vacuum insert threshold = vacuum base insert threshold + vacuum insert scale factor * number of tuples
+</programlisting>
+    where the vacuum insert base threshold is
+    <xref linkend="guc-autovacuum-vacuum-insert-threshold"/>,
+    and vacuum insert scale factor is
+    <xref linkend="guc-autovacuum-vacuum-insert-scale-factor"/>.
+    Such vacuums may allow the table's <structfield>relfrozenxid</structfield>
+    to be advanced and will reduce the chances of and the impact of any
+    aggressive vacuums.
+    The number of obsolete tuples and the number of inserted tuples are
+    obtained from the statistics collector; it is a semi-accurate count updated by each
+    <command>UPDATE</command>, <command>DELETE</command> and
+    <command>INSERT</command> operation.  (It is only semi-accurate because
+    some information might be lost under heavy load.)  If the
+    <structfield>relfrozenxid</structfield> value of the table is more
     than <varname>vacuum_freeze_table_age</varname> transactions old, an aggressive
     vacuum is performed to freeze old tuples and advance
     <structfield>relfrozenxid</structfield>; otherwise, only pages that have been modified
     since the last vacuum are scanned.
-    Finally, a threshold similar to the above is calculated from
-    <xref linkend="guc-autovacuum-vacuum-insert-threshold"/> and
-    <xref linkend="guc-autovacuum-vacuum-insert-scale-factor"/>.
-    Tables that have received more inserts than the calculated threshold
-    since the last <command>VACUUM</command> will also be vacuumed.
    </para>
 
    <para>
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index b4974a5f20..b7c526abc3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -3545,7 +3545,7 @@ static struct config_real ConfigureNamesReal[] =
 			NULL
 		},
 		&autovacuum_vac_ins_scale,
-		0.0, 0.0, 1e10,
+		0.01, 0.0, 1e10,
 		NULL, NULL, NULL
 	},
 
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index cc3df73a82..9988fe40f5 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -604,7 +604,7 @@
 #autovacuum_analyze_threshold = 50	# min number of row updates before
 					# analyze
 #autovacuum_vacuum_scale_factor = 0.2	# fraction of table size before vacuum
-#autovacuum_vacuum_insert_scale_factor = 0.0	# fraction of table size before
+#autovacuum_vacuum_insert_scale_factor = 0.01	# fraction of table size before
 					# vacuum
 #autovacuum_analyze_scale_factor = 0.1	# fraction of table size before analyze
 #autovacuum_freeze_max_age = 200000000	# maximum XID age before forced vacuum