CROSSTAB( .. only one column has values... )

I'm using the crosstab feature and do not understand why I am only
getting values in the first column.

The query:
SELECT 
  date_trunc('month', t2.value_date) AS invoice_date, 
  t1.value_string AS invoice_type
  COUNT(*)
FROM document d
  LEFT OUTER JOIN obj_property t1
    ON (t1.obj_id = d.document_id
        AND t1.namespace_prefix = 'http://www.example.com/ctabs'
        AND t1.value_key = 'invoiceType')
  LEFT OUTER JOIN obj_property t2
    ON (t2.obj_id = d.document_id
        AND t2.namespace_prefix = 'http://www.example.com/ctabs'
        AND t2.value_key = 'invoiceDate')
WHERE ((d.project_id = 1134510213) AND (d.is_folder = 0))
GROUP BY 1,2

 - has results like -

invoice_date invoice_type count 
------------ ------------ ----- 
2013-02      service      3454  
2013-03      service      3512  
2013-03      parts        5366  
2013-04      parts        5657  
2013-04      service      4612  
2013-05      service      4946  
2013-05      parts        5508  
...

So I put this in as a crosstab:

SELECT * FROM crosstab(
    $$
SELECT 
  SUBSTR(t2.value_string, 1, 7) AS invoice_date,
  t1.value_string AS invoice_type,
  COUNT(*)
FROM document d
  LEFT OUTER JOIN obj_property t1
    ON (t1.obj_id = d.document_id
        AND t1.namespace_prefix = 'http://www.example.com/ctabs'
        AND t1.value_key = 'invoiceType')
  LEFT OUTER JOIN obj_property t2
    ON (t2.obj_id = d.document_id
        AND t2.namespace_prefix = 'http://www.example.com/ctabs'
        AND t2.value_key = 'invoiceDate')
WHERE ((d.project_id = 1134510213) AND (d.is_folder = 0))
GROUP BY 1,2
 $$) AS final_result (invoice_date VARCHAR, "parts" BIGINT, "rental"
BIGINT, "sales" BIGINT, "service" BIGINT);

 - and I get the results of -

invoice_date parts rental sales  service 
------------ ----- ------ ------ ------- 
2001-09      1     (null) (null) (null)  
2007-07      1     (null) (null) (null)  
2013-02      5353  (null) (null) (null)  
2013-02      3454  (null) (null) (null)  
2013-03      3512  (null) (null) (null)  
2013-03      5366  (null) (null) (null)  
...

Only the first column has values, all the rest are NULL.
I assume I am missing something stupid.

-- 
Adam Tauno Williams <mailto:awilliam@whitemice.org> GPG D95ED383
Systems Administrator, Python Developer, LPI / NCLA