This article uses workplace level data from the recent Australian Work
place Industrial Relations Survey to test a simple demand and supply m
odel explaining the level of union membership within Australia. The fi
ndings suggest that previous research using individual-level data has
understated the importance of the supply-side in influencing union mem
bership. In particular, unionization levels were found to be highly se
nsitive to firm size, to the number of unions represented in the workp
lace and to management attitudes