Labour force participation rates are falling around the world signalling the slack employment growth that has accompanied the aftermath of the Global Financial Crisis. It is clear that many workers are opting to stop searching for work while there are not enough jobs to go around. As a result, national statistics offices classify these workers as not being in the labour force, which had had the effect of attenuating the official estimates of unemployment and unemployment rates. These discouraged workers are considered to be hidden unemployment. But the participation rates are also influenced by compositional shifts (changing shares) of the different demographic age groups in the working age population. In most nations, the population is shifting towards older workers who have lower participation rates. Thus some of the decline in the total participation rate could simply being an averaging issue – more workers are the average who have a lower participation rate. This blog investigates that issue for Australia as part of a project aiming to get more accurate measures of hidden unemployment.