Field experiments in labor economics

In this thesis I show with three studies how field experiments can enhance our understanding of labor markets. Economists traditionally assume that individuals exclusively respond to monetary incentives. As a consequence, if workers have no prospect of future employment at the firm and pay is not contingent on their performance, a wage change should not affect effort. Some economists, however, have recognized that this narrow view of human motivation may severely limit our progress in understanding incentives. In Chapters 2 and 3, I investigate the role of psychological motives like the desire to reciprocate in the context of a real‐life work environment. The first experiment explores the impact of a wage increase on work performance when there is no economic reason for workers to change their effort. I find that workers reciprocate a generous wage with higher performance, particularly those workers who care about fairness and felt underpaid prior to the wage increase. The second experiment investigates the effects of a wage cut on performance when either all workers in a team or only some of them suffer the cut. I show that a general pay cut reduces performance, while a wage cut for only some of the workers reduces their performance more than twice as much. This finding demonstrates the powerful force of social comparison and the need to build the social nature of humans into economic theory. In Chapter 4, I examine the joint effects of monetary incentives and social interaction on work performance. Many jobs offer wage schemes that create positive or negative externalities on coworkers. Whether or not workers have the possibility to interact socially at work may distort the intended incentives of these schemes. I find that under relative incentives, when own effort imposes a negative externality on the coworker’s income, social interaction works against monetary incentives and leads to low performance due to collusion. However, the more workers differ in skills the less able they are to sustain collusive agreements. In der vorliegenden Dissertation zeige ich anhand von drei Studien wie Feldexperimente unser Verständnis von Arbeitsmärkten verbessern können. Ökonomen gehen traditionell davon aus, dass Individuen ausschliesslich auf materielle Anreize reagieren. Wenn also Arbeitskräfte keine Aussicht auf eine langfristige Anstellung haben und deren Lohn nicht von der Leistung abhängt, dann sollte eine Lohnveränderung keinen Einfluss auf die Arbeitsleistung haben. Manche Ökonomen haben jedoch erkannt, dass diese Sichtweise des menschlichen Verhaltens beschränkt ist und unseren Fortschritt im Verständnis von Anreizen bremsen kann. In den Kapiteln 2 und 3 untersuche ich die Bedeutung von psychologischen Motiven wie Fairness oder Reziprozität in echten Arbeitsumgebungen. Das erste Experiment untersucht den Einfluss einer Lohnerhöhung auf die Arbeitsleistung, wenn Arbeitskräfte keinen ökonomischen Grund haben, ihren Arbeitseinsatz zu ändern. Diese Studie zeigt, dass Arbeitskräfte einen grosszügigen Lohn mit höherer Arbeitsleistung erwidern. Dies gilt besonders für diejenigen, die Fairness als wichtig empfinden und sich vor der Lohnerhöhung unterbezahlt fühlten. Das zweite Experiment untersucht die Wirkung einer Lohnkürzung auf die Arbeitsleistung, wenn entweder das ganze Team oder nur einen Teil davon betroffen ist. Diese Studie zeigt auf, dass eine generelle Lohnkürzung die Arbeitsleistung senkt, wohingegen eine Lohnkürzung nur für einzelne Arbeitskräfte deren Leistung um mehr als das Doppelte reduziert. Diese Erkenntnis unterstreicht die Bedeutung von sozialen Motiven und die Notwendigkeit einer Veränderung des Menschenbilds in der Ökonomie. In Kapitel 4 erforsche ich den gemeinsamen Einfluss von materiellen Anreizen und sozialer Interaktion auf die Arbeitsleistung. Viele Firmen bieten Lohnsysteme an, bei welchen die eigene Leistung vor‐ oder nachteilhafte Nebeneffekte auf das Einkommen der Arbeitskollegen hat. Soziale Interaktion am Arbeitsplatz kann dabei die Anreize dieser Lohnsysteme verzerren. Diese Studie findet heraus, dass bei Entlohnung der Arbeitskräfte durch Turnieranreize, d.h. wenn die eigene Leistung sich nachteilhaft auf das Einkommen der Arbeitskollegen auswirkt, soziale Interaktion die Anreize ausser Kraft setzt und zu geheimen Absprachen führt. Wenn hingegen Arbeitskräfte sehr unterschiedliche Fähigkeiten besitzen, dann sind geheime Absprachen schwieriger aufrecht zu halten

FDG-PET/CT imaging using an intravenous drip injection of scopolamine butylbromide as an inhibitor of normal uptake in the intestines

Society of nuclear medicine 53rd Annual Meetn

FDG-PET/CT imaging using an intravenous drip injection of scopolamine butylbromide as an inhibitor of physiologic uptake in the stomach

Society of nuclear medicine 54rd Annual Meetn

Carbon-11-methionine PET Imaging of Choroidal Melanoma before and after Proton Beam Radiotherapy

PURPOSE:Choroidal melanomas shrink slowly after radiotherapy but do not disappear completely in general. Moreover, histological evaluation after therapy cannot be made except for the case of enucleation. Therefore, another rvaluation method in addition to the measurement of tumor size is desirable. The purpose of this study is to assess the ability of Carbon-11-methionine PET (MET PET) to detect choroidal melanoma lesion and the feasibility of MET PET as an evaluation method of therapeutic effect in proton beam radiotherapy.METHOD AND MATERIALS:We studied consecutive six patients with choroidal malignant melanoma treated with proton beam therapy in 2001-2002. The mean follow up time was 22.2 months (ranged from 12 to 32 months). All patients underwent at least three MET PET scans, before therapy, one month after therapy and about six after therapy. And some patients underwent further follow up MET PET scans. Three patients underwent fourth MET PET about 12 months after therapy, and three patients underwent fifth (two patients, forth) MET PET about 24 months after therapy. MRI was performed one week within each MET PET scan. We evaluated the lesion semiquantitatively on the basis of the Tumor-To-Brain Ratio (TBR).RESULTS:No patients in this study showed tumor regrowth or local recurrence to date. Alll choroidal lesions were positive on MET PET before therapy. Mean TBR before therapy was 1.29±0.31(n=6), and did not changed at one month after therapy (p=0.987). But,mean TBR decreased to 0.77±0.23 (n=6) 6 months after therapy (p=0.003) and additionally decreased to 0.39±0.24 (n=3) 12 months after therapy (p=0.033). Mean TBR 24 months after therapy was not almost changed (0.41±0.18) compared with that 12 months after therapy. In respect of visual evaluation, all MET uptake disappeared 12 and 24 months after therapy. On the other hand, mean tumor size showed only 27.5% decrease even 24 months after therapy.CONCLUSION:Carbon-11-methionine is considered to be a useful tracer to detect choroidal melanoma. MET PET after proton beam radiotherapy may be a valuable method to evaluate the effect of proton beam radiotherapy.RSNA2004 90th Scientific Assembly and Annual Meetin

Gastric Cancer Found on 3\u27-Deoxy-3\u27 F-18 Fluorothymidine Positron Emission Tomography

We report a case of gastric cancer that was incidentally found on 3\u27deoxy-3\u27F-18fluorothymidine (FLT) positron emission tomography (PET). FLT PET has the potential utility for noninva-sively measuring cellular proliferation in vivo in many malignant tumors. A 68-year-old male with squamous cell carcinoma of the left upper lung was treated by carbon ion radiotherapy (CIRT; 52.8 GyE./4 fractions). To evaluate the response of the lung cancer to CIRT, an FLT PET/CT study was performed before and 3 months after CIRT. Very intense focal uptake of FLT in the gastric wall on PET images obtained 3 months after CIRT raised the suspicion of gastric malignancy. Endoscopic examination revealed an advanced gastric cancer (tubular adenocarcinoma, well to moderately differ-entiated) at the site of intense FLT uptake