The auto optimizer stats isn't working correctly.

  We have a Warehouse database, and I have noticed that the rows in some particular tables have increased significantly but the automated gather stats job has not analyzed stats for these tables. For example, one table has increased from 10 millions to 22 million rows, the last_analyzed is 19th April 2010. I have checked the optimizer job is running and it does every night, see below: CLIENT_NAME                                                      JOB_STATUS
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JOB_START_TIME
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JOB_DURATION
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auto optimizer stats collection                                  SUCCEEDED
28-FEB-11 22.00.02.231000 EUROPE/LISBON
+000 00:05:42

auto optimizer stats collection                                  SUCCEEDED
01-MAR-11 22.00.02.229000 EUROPE/LISBON
+000 00:04:50

auto optimizer stats collection                                  SUCCEEDED
02-MAR-11 22.00.01.397000 EUROPE/LISBON