pg_dump issues

Hi All,

I have a database with only one schema with 5 tables 

nspname |       relname           |  size

     ---------+---------------------+---------

     sch     | job1                      | 211 MB

     sch     | job2                      | 5611 MB

     sch     | job3                      | 6584 kB

     sch     | job4                      | 89 MB

     sch     | job5                      | 39 MB

Total sum of sizes of the table is less than 6 GB.

When I do a pg_dump of this database it is 20GB (I also did a pg_dump of only schema data and the size was still the same). I am using postgres 8.4.1 version.

Could any one explain why the pg_dump size of the file is 3 times the size of the tables?

Thanks

Deepak