Rates are calculated for Indigenous and non-Indigenous.

Rate ratios and rate differences are calculated for Indigenous: non-Indigenous.

For variability bands: More work is to be undertaken by the AIHW regarding the use of variability bands for perinatal data for COAG reporting.

For trends: percentage change and statistical significance of change is to be calculated (required for CRC reporting).

Presentation:

Number, rate per 100 infants (percentage), rate ratio and rate difference.

'Low birth weight' is defined as less than 2500 grams.

Excludes multiple births, stillbirths, and births with unknown birthweight.

Analysis by state/territory is based on the usual residence of the mother.

Excludes Australian non-residents of external territories and where state/territory of residence was not stated.

Rate: 100 x (Numerator ÷ Denominator).

Rate ratio: Indigenous rate divided by non-Indigenous rate.

Rate difference: Indigenous rate minus non-Indigenous rate.

Percentage change: Calculated by multiplying the average annual change over the period by the number of data points less 1. This is then divided by the rate for the first year in the series and multiplied by 100.

The average annual change in rates, rate ratios and rate differences are calculated using linear regression which uses the least squares method to calculate a straight line that best fits the data and returns an array that best describes the line. The simple linear regression line, Y = a + bX, or ‘slope’ estimate was used to determine the average annual change in the data over the period. The formula used to calculate the slope estimate and standard error of the slope in Microsoft Excel is:

LINEST: (known_y’s, known_x’s, true) entered as an array formula (Ctrl, Shift, Enter).

Statistical significance of change:  More work to be undertaken by the AIHW regarding the use and methodology for statistical significance of change for perinatal data.

Current Period – (2007-2009):

For Indigenous and non-Indigenous (number, rate, rate ratio, and rate difference):

• National and state/territory by Indigenous status

Time series–2007, 2008 (previously supplied); 2009 (required for 2012 reporting):

For Indigenous and non-Indigenous (number, rate, rate ratio, rate difference, and percentage change. Variability bands and statistical significance of change to be advised by the AIHW):

• National and state/territory by Indigenous status.

Most recent data available for 2012 CRC report is 2009.

Aggregated data (2007 to 2009) will be reported for the current reporting period.

Single year data (2007, 2008 and 2009) will be reported for time series; noting that previously supplied data will be used unless a resupply is provided.

Information is included in the National Perinatal Data Collection (NPDC) for all live births and still births of at least 400 grams birthweight or at least 20 weeks gestation

Currently available data on Indigenous status of infants is based solely on the Indigenous status of the mother.

Disaggregation by Indigenous status is recommended to be reported using three-year combined data for the current reporting period due to the small number of low birthweight infants born to Indigenous mothers each year. Single year data is to be reported for time series.

To report trends, the COAG Reform Council will separately request percentage change and statistical significance testing for this indicator directly from the data provider (AIHW).

More work is to be undertaken by the AIHW regarding the use of variability bands for perinatal data for COAG reporting.

Baseline year for NIRA target (Halve the child mortality gap within a decade) is 2008; baseline year for this indicator is 2008; target year is 2018.

Specification: Long-term.

A data item for Indigenous status of the baby will be added to the perinatal NMDS for collection from July 2012 onwards.