If I'm understanding correctly how the data is structured I think you will need to define a custom SQL connection giving you the union of all of your tables, rather than trying to use data blending - you can't use data blending to merge data from different years like that.
A union query will work easily if your table structures are identical - i.e. if they have the same number of type of fields and the same field names. If there are slight differences you might have to do some slight tweaks.
The easiest way to generate the custom SQL query if the tables are indeed identically structured is just to selecting one of the tables you want as a single table connection, then switch over to a Custom SQL connection. That will be pre-populated with a query for all fields in that table. Coopy the text of that query into a text editor and append a line saying "UNION ALL".
The switch back to your Tableau window and change the connection back to a single table connection. Select the second table you want to merger, then change the connection back to a Custom SQL connection. Copy the SQL statement for the second table and paste it onto the bottom of your first one, appending another "UNION ALL" line.
Keep going till you have a query which merges all of your tables (you mustn't have a UNION ALL line after the last table).
Finally copy the query and paste it into the Custom SQL window and complete defining the connection. Be warned that if there are any differences or you make any slight mistakes in the editing you may get fairly misleading erorr messages.
This worked perfect. Thank you so much!!
There were actually two or three extra fields in the new tables that I didn't know were added. However, all I did was erase them from the Custom SQL code and it worked great. Now I see all data for 2005-2012 in the same table!!