I think they should calculate employment/unemployment rates by different, more realistic measures. Instead of trying to make casuals and part-timers fit one category or the other as described by lionking (which is so 1950's thinking in Australia...thanks, Johnny Howard!).
For example, "unemployment rate" could be defined as "the ratio over a period of time of available work-hours not being used versus available work-hours in use." The "available work-hours not being used" would take into account part-time people who are out of work just as much as full-time people. It could exclude people who are simply not available to work, and could be used as a criteria for determining a person's work availability. The obvious intention is to try to make the ratio as close to 1 as possible.
For example, if I retire, I may wish to keep working but at a reduced level. So I could be available to work 10 hours per week rather than the ridiculous hours I do now. If I'm in work, those 10 hours count towards "available work-hours in use". If not employed, they contribute towards "available work-hours not being used". If I then decide I don't wish to be employed at all, I can make my available work hours zero, thus not contributing to the ratio calculation at all. Although perhaps my work benefits would be reassessed appropriately too.