In the last decades, in most of the OECD countries employment relations have been changing and atypical forms of employment have been spreading rapidly. The “standard contract”, permanent and full-time, has lost importance, replaced by “flexible jobs”, such as fixed-term contracts, temporary work agency employment, variable working hours jobs, on call employment. A debate has been rising on whether atypical jobs, especially short-term contracts, might spur the development of a secondary labour market, in which the unemployed might get trapped in a cycle between dead-end jobs and unemployment. On the other hand, disadvantaged groups excluded from employment by too strict regulations might benefit most from the enhanced flexibility. Chapter 1 introduces this debate, Chapters 2 and 3 shed light on it. I analyse the labour market performance of workers who left unemployment through short-term jobs. I infer what counterfactual labour market performance would have been undertaken if the unemployed had rejected these jobs. In this way, it can be established whether short-term jobs may increase or decrease the chances of having a more stable career later in life, i.e. whether they are “stepping stones” or “dead ends”. I find evidence supporting the stepping stone hypothesis both in Italy and in Belgium. In terms of future job stability, even precarious and unsuccessful jobs are to be preferred to longer searches for directly finding better jobs. Chapter 4 is an identification analysis of the econometric models for duration data that encompass competing risks of exits, consecutive spells, and lagged duration dependence. Finally, Chapter 5 provides a new estimation strategy to look at the effect of past labour market experiences on two aspects of the subsequent job quality: wage and tenure on the job. The methodological novelty consists in jointly modelling labour market durations, transitions, and wages by way of a hazard-function based approach.

在台灣，臨時性雇用佔總就業比例在2012年大約為5.3%，而且這個比例近年來有持續上升的趨勢。當勞工的工作型態從臨時性轉換到非臨時性雇用或是從非臨時性轉換到臨時性雇用時，勞工的薪水會因此而有明顯地差距。本研究利用人力運用調查之下的擬追蹤資料，檢驗勞工改變其工作型態與其薪水變化之間的關係。實證結果顯示從臨時性轉換到非臨時性工作之勞工，其薪水有顯著地上升；而從非臨時性轉換到臨時性工作之勞工，其薪水會受到顯著地傷害。女性從臨時性轉換到非臨時性工作，可以享有較多的薪水增加，但是男性從非臨時性轉換到臨時性工作時，薪水會受到較多的傷害。而年齡介於40至60歲之間的勞工，薪水下降較其他年齡層的勞工多；而較年輕的勞工其薪水增加較多。 / In Taiwan, the proportion of temporary employment is about 5.3% (as of 2012) and this ratio has been growing gradually in recent years. Wage differences are caused by change of job status from non-temporary to temporary and vice-versa. Using data from the Manpower Utilization Quasi-Longitudinal Survey, the results confirm that workers switching from non-temporary to temporary jobs suffer significant erosion of income and workers switching from temporary jobs to non-temporary jobs receive significant income gain. Women benefit more when changing from temporary employment to non-temporary, while men suffer more when transiting from non-temporary to temporary jobs. The wage loss for workers’ in age group 40 to 50 is larger than workers in other age groups and younger workers receive greater income gains.