Before/After Trigger efficiency

Something changes continuously... and trigger efficiency too :).
Please compare Oracle statement about triggers (see "Note" about trigger efficiency)
Oracle 9i, Oracle 10g and Oracle 11g.

I`ve tested this on 11.1.0.7 (the only database version in my hands now).
Its behavior matches 11g and 9i documents.

I used triggers with empty body like this:

create or replace trigger t1_tr_bu
before update on t1
for each row
begin
null;
end;
/

create or replace trigger t1_tr_au
after update on t1
for each row
begin
null;
end;
/


and receive these results:
without triggers



1 row updated.


Statistics
----------------------------------------------------------
 0  recursive calls
 1  db block gets
 7  consistent gets
 0  physical reads
352  redo size
674  bytes sent via SQL*Net to client
591  bytes received via SQL*Net from client
 3  SQL*Net roundtrips to/from client
 1  sorts (memory)
 0  sorts (disk)
 1  rows processed

with before trigger




1 row updated.


Statistics
----------------------------------------------------------
 0  recursive calls
 2  db block gets
 7  consistent gets
 0  physical reads
296  redo size
674  bytes sent via SQL*Net to client
591  bytes received via SQL*Net from client
 3  SQL*Net roundtrips to/from client
 1  sorts (memory)
 0  sorts (disk)
 1  rows processed

with after trigger

1 row updated.

Statistics

----------------------------------------------------------

 0  recursive calls

 1  db block gets

 7  consistent gets

 0  physical reads

 0  redo size

674  bytes sent via SQL*Net to client

591  bytes received via SQL*Net from client

 3  SQL*Net roundtrips to/from client

 1  sorts (memory)

 0  sorts (disk)

 1  rows processed