Setting
Within the Dutch system of medical care most medical specialists work in a hospital setting, although they are usually not employed by the hospital. The majority are self-employed, working with other specialists of the same speciality in a partnership. A partnership can be defined as an organisational structure in which all partners are equals, mutually dependent, have a common goal, and generate their own income. Although partnerships are relatively independent entities, they can only exist within the context of the hospital. In the same way, hospitals cannot exist without medical specialists [29]. In 2000 71% of the medical specialists in The Netherlands were self-employed [29], in 2002 this figure was 75% [30]. A small proportion of medical specialists were employed by the hospital, usually working in academic hospitals.
Study population
Data used in this article consist of two samples: data from a survey conducted in 1996 and data from a survey conducted in 2004.
Survey 1996
Among other groups of medical specialists, specialists in internal medicine working in general and academic hospitals in The Netherlands participated in this study. A stratified random sample was drawn from the professional register. In order to ensure that enough part-time working respondents participated, the proportion of female respondents was raised. The resulting sample consisted of 615 specialists in internal medicine. They were sent a questionnaire, including topics on the attitude towards working part-time and the time invested in work. The response was 63% (n = 390) and did not vary much with respect to gender. To be able to compare the chartacteristics of the 1996 sample to those of the 2004 sample, a weight factor for gender was composed, thereby correcting for the high number of females due to the specific method of sampling. These weighted data were used when describing the characteristics of the sample.
Survey 2004
Three different groups of specialists, including specialists in internal medicine, participated in this study. A questionnaire was sent to all specialists in internal medicine working in general hospitals in The Netherlands (n = 817). Among other topics, questions were asked about attitudes towards working part-time and the time invested in work. The response was 53% for internal medicine specialists (n = 411).
Since work arrangements in academic hospitals differ fundamentally from those in general hospitals, the focus of this study was solely on specialists in internal medicine working in general hospitals in The Netherlands. Therefore, 171 specialists in internal medicine of the 1996 sample and 9 specialists in internal medicine of the 2004 sample working in academic hospitals were excluded. For 39 specialists of the 2004 sample it was unknown whether they worked part-time or full-time. Consequently, they were excluded from analyses as well. After exclusion, the final sample consisted of 219 specialists in internal medicine in 1996 and 363 specialists in internal medicine in 2004.
The responding specialists in internal medicine in 1996 were compared to the population of specialists in internal medicine in 1996 with respect to gender and age. In our 1996 sample 84% of the specialists were male. For the population in 1996 this figure was 82%. With respect to age, specialists in internal medicine in our 1996 sample were slightly underrepresented in the two highest age categories (60–64 years and 65 years and older), but the differences were small. The proportion of part-time workers was not available for the population of 1996. However, the number of hours worked per week showed no significant difference between responding specialists (54.2 hours) and the population (56 hours). In our 1996 sample 56% worked in a general hospital; for the population this figure was 55%. The 1996 sample, thus, seems representative for the population in 1996. Due to a lack of information about the population of internal medicine specialists in 2004, we were not able to see whether our 2004 sample was representative for the population of internal medicine specialists working in general hospitals.
Measures
Background variables
Background variables included in this study were gender and age. Age was classified into four categories: ≤ 34 years, 35–44 years, 45–54 years and ≥ 55 years. Besides these socio-demographic characteristics, the actual time invested in work (in hours), was included as a background variable. For this purpose questions were asked about the average number of hours the specialists in internal medicine worked weekly. Time invested in work was classified into three categories: < 25 hours, 25–50 hours and 50–80 hours a week.
Full-time or part-time
To determine whether an internal medicine specialist worked part-time or full-time, in both studies questions were asked about the formal time worked, expressed in full-time equivalents (FTE). Part-timers were defined as working less than 1,0 FTE and full-timers as working 1,0 FTE.
Attitudes towards working part-time
Part-time attitude was measured with 10 items using a five-point Likert-scale in 1996 (1 = I fully agree, 3 = partly agree, partly disagree and 5 = I fully disagree) and a three-point scale in 2004 (1 = I fully agree, 2 = partly agree, partly disagree and 3 = I fully disagree). The scale was devised in 1996 on the basis of 20 interviews with medical specialists in The Netherlands, concerning the (positive and negative) consequences of part-time work. The resulting scale covered different aspects of the attitude towards working part-time such as consequences of working part-time for the quality of care, consequences of working part-time for one's individual career, and consequences of working part-time for the organisation (e.g. 'If the proportion of part-time doctors increases, the flexibility of task division will be higher'). The mean score on the 10-item scale reflects an overall attitude towards part-time work. The internal consistency of the 10-item scale in both studies was high (Cronbach's alpha .77 in both studies). In order to be able to compare the 1996 data with those from 2004, the scores from 1996 were recoded into a three-point scale similar to the one used in 2004 (score 1, 2→1, score 3→2 and score 4, 5→3).
Analyses
To answer the first research question concerning the possible changes in attitudes in time, the mean attitude towards working part-time was calculated for full-time working specialists and part-time working specialists in 1996 and 2004. Differences in attitudes between full-timers and part-timers and between 1996 and 2004 were tested using Analysis of Variance (ANOVA). To examine the relationship between individual characteristics and the attitudes towards part-time work (second research question), two more Analyses of Variance were performed: one for 1996 and one for 2004. In both analyses, working part-time was taken as a factor and gender, age and time invested as covariates. The unweighted data were used in these analyses.
The third research question, concerning the degree of resemblance in internal medicine specialists' attitudes within partnerships, was examined by calculating the Intra Class Correlation (ICC). For this purpose multilevel analyses were performed, using Mlwin. With multilevel analyses the total variation is separated in different parts: a part due to differences between medical specialists and another part due to differences between partnerships [31]. The ICC was calculated for the sample of 2004. In addition, covariates that proved to be significant from the ANOVA's were taken in account. For the specialists in internal medicine of the 1996 sample, however, no information was available as to what partnership individual specialists participated in. Therefore, it was not possible to examine the degree of resemblance in attitudes within partnerships for the sample of 1996.