Total 'units of activity' are derived from the National Hospital Cost Data Collection Round 16 (2011-12). This collection is managed by the Independent Hospital Pricing Authority. The full dataset specification can be found at http://www.ihpa.gov.au/internet/ihpa/publishing.nsf/Content/nat-hosp-cost-data-collection-round-16

Total 'units of activity' form the denominator of the National Health Performance Authority's Comparable Cost of Care indicator.

Hospital admissions are in-scope for Comparable Cost of Care and Total 'units of activity' if:

• The patient is classified as an acute admission
• The patient was admitted and discharged within the 2011-12 financial year
• The patient has a non-error AR-DRG 6.x

Total 'units of activity' is derived as the sum of weighted separations as calculated for the Comparable Cost of Care indicator.

• A weighted separation is derived as;

Weighted Separation = [ CW x (A_Paed x (1 + A_SPA) x ( 1 + A_Ind + A_{A +}A_RT) + (A_ICU x ICU_Hrs ))]

Where:

• CW means the Base Cost Weight

i.e. Average comparable cost for a AR-DRG divided by average comparable costs for all AR-DRGs [where weights are calculated using data from major and large hospitals with an emergency department providing data to the NHCDC, and total in-scope costs only]

• A_Paed means the paediatric adjustment
• A_SPA means the specialist psychiatric age adjustment
• A_Ind means the indigenous adjustment
• A_A means the remoteness area adjustment
• A_RT means the radiotherapy adjustment
• A_ICU means the ICU adjustment
• ICU_Hrs Means the number of hours spent by a person within a Level 3 ICU/PICU 

For the purpose of deriving the Base Cost Weights, the following costs are deemed to be in-scope: