There are three missing documents which should have been published with the NPPF but have not.
1. The Summary of Consultation Responses
The consultation report is always published on the same day as the policy itself right back to the days of PPS1.
2. The Final Impact Statement
The draft contains lots of assumptions about greenfield land loss, which were quickly discredited, so what are the assumptions now?
3. The Government Response to the DCLG Select Committee Report
The government has published a press release that it has issued a response, but the select committee itself has not published it.
Managing the news agenda by not publishing bad news until after the Easter Recess if at all? After all the consultation report will likely show the most overwhelmingly negative response of any recent government consultation, even the NHS reforms. To achieve a result in parliament and the press the DCLG would not want these coming out the same day would they?
Decisions, Decisions, Decisions 
> 2. The Final Impact Statement
http://www.planningportal.gov.uk/uploads/pins/advice_for_inspectors/nppf.pdf includes an Annex on “Changes listed in National Planning Policy Framework Impact assessment” (but not the actual impact assessment).
> 3. The Government Response to the DCLG Select Committee Report
How about http://www.official-documents.gov.uk/document/cm83/8322/8322.asp ?
Of course the first is not the impact assessment.
Thanks for the Select reponse, select committee just had not got around to a link