When women work voluntarily part-time, on the labour force survey there are follow-up questions. It asks what the reasons were for the voluntary part-time and whether it was for care of family. So you can look beyond just the voluntary and involuntary; you can look at more details for the voluntary part-time. It's definitely possible, but we don't have that information here today.
On May 26th, 2009. See this statement in context.