This Report is about measuring temporary populations, in contrast to the permanent population measured by the Census undertaken by the Australian Bureau of Statistics (ABS) every five years. In particular, its main aim is to quantify the temporary populations associated with holiday homes along the Australian coastline, situated in so called sea change localities, defined generally as those areas becoming increasingly popular as retirement centres for baby boomers in particular. As well, the Report undertakes an extensive analysis of data collected by the regular Survey of Tourist Accommodation (STA) also undertaken by the ABS to determine the impact of tourist accommodation in sea change local government areas on their temporary population. Temporary populations are on the rise worldwide. They have both spatial (they have different dimensions in different locations) and temporal (they vary from time to time) components. Holiday homes are a powerful source of temporary populations because of their occasional use, and the size of this population is largely unmeasured because a large proportion of them are unoccupied at the time of the Australian Census. In the Local Government Authorities (LGAs) on which this report is based1 , the proportion of unoccupied dwellings in 2006 was 9.8 percent, but this level rose to 10.2 percent at the 2011 Census. There is wide variation between LGAs, generally depending on their winter climate. So, in Cairns the proportion of unoccupied dwellings in 2011 was 10.1 percent, while for the Surf Coast in Victoria it was 42.0 percent.