In this light it is intersting to note that the most reliable employment data source, the ES-202 (quarterly unemplyment insurance data that are near-census quality) gives information only on total number of persons employed and wages - it does not give the number of hours worked. The latter are collected on a survey-basis, which typically includes only non-surpervisory employees (at least in MD, the state I'm most familiar with) - the labour market segment most affected by part-time jobs. At the same time, there is plenty of anecdotal evidence of "supervisory" (read: white collar workers) working longer hours without overtime.
Another point - the term "leisure time" is misleading - a great chunk of this time can be more appropriately described as "consumer work" i.e. time spent on purchasing consumer goods, and "commuter work" i.e. time spent on commuting to the places of employment ond consumer work. If we factor the consumer and commuter work out, the actual amount of leisure (i.e. truly disposable free time) shrinks quite considerably.
Wojtek