Essays in Labour and Urban Economics

This thesis contains three essays that focus on topics in labour and urban economics. In Chapter 1, I use new administrative Canadian matched owner-employer-employee data to investigate the mechanisms that drive entry into entrepreneurial careers and entrepreneurial success among young individuals. I pay particular attention to the value of prior work experience in entrepreneurship. I use information on the career choices and earnings of individuals each year to structurally estimate a dynamic Roy model of career choice. I recover parameters governing: (a) the returns to various types of experience in the labour market and in entrepreneurship, (b) the non-pecuniary benefits associated with being a worker and an entrepreneur, and (c) career-specific entry costs. I use the estimated model to evaluate the impact of policies designed to promote successful entrepreneurship. Chapter 2 (joint with Leah Brooks and Gisela Rua) investigates how containerization impacts local economic activity. Containerization is premised on a simple insight: packaging goods for waterborne trade into a standardized container makes them dramatically cheaper to move. We use a novel cost-shifter instrument -- port depth pre-containerization -- to contend with the non-random adoption of containerization by ports. Container ships sit much deeper in the water than their predecessors, making initially deep ports cheaper to containerize. Consistent with New Economic Geography models, we find that cities near container ports grow an additional 70 percent from 1950 to 2010. Gains predominate in cities with initially low population density and manufacturing. Chapter 3 (joint with Marco Gonzalez-Navarro, Stefano Polloni, and Matthew Turner) investigates the relationship between the opening of a city's subway network and its air quality. We find that particulate concentrations drop by 4% in a 10km radius disk surrounding a city center following a subway system opening. The effect is larger near the city center and persists over the longest time horizon that we can measure with our data, about eight years. We estimate that a new subway system provides an external mortality benefit of about $594m per year. Although available subway capital cost estimates are crude, the estimated external mortality effects represent a significant fraction of construction costs.Ph.D

Prior Work Experience and Entrepreneurship: The Careers of Young Entrepreneurs

I investigate the mechanisms that drive sorting into entrepreneurship and entrepreneurial success among young individuals. I use Canadian matched owner-employeremployee data to conduct my investigation. Empirically, older entrepreneurs and entrepreneurs who have previously worked in high-wage firms tend to do better. To explain these findings, I develop a dynamic Roy model of career choice that features heterogeneous employers, human capital accumulation, and unobserved heterogeneity across individuals. Among other things, I find that prior work experience is particularly valuable for "subsistence" entrepreneurs. I use the estimated model to evaluate policies designed to promote entrepreneurship

Subways and Urban Air Pollution.

We investigate the effect of subway system openings on urban air pollution. On average, particulate concentrations are unchanged by subway openings. For cities with higher initial pollution levels, subway openings reduce particulates by 4 percent in the area surrounding a city center. The effect decays with distance to city center and persists over the longest time horizon that we can measure with our data, about four years. For highly polluted cities, we estimate that a new subway system provides an external mortality benefit of about $1 billion per year. For less polluted cities, the effect is indistinguishable from zero. Back of the envelope cost estimates suggest that reduced mortality due to lower air pollution offsets a substantial share of the construction costs of subways

The G protein-coupled P2Y6 receptor promotes colorectal cancer tumorigenesis by inhibiting apoptosis

Colorectal tumors are immersed in an array of tumor-promoting factors including extracellular nucleotides such as uridine 5′‑diphosphate (UDP). UDP is the endogenous agonist of the G protein-coupled P2Y6 receptor (P2Y6R), which may contribute to the formation of a tumor-promoting microenvironment by coordinating resistance to apoptosis. Colorectal cancer (CRC) was chemically induced in P2ry6 knockout (P2ry6−/−) mice using azoxymethane and dextran sulfate sodium challenges. Mice were euthanatized and their tumor load determined. Fixed tissues were stained for histological and immunohistochemistry analysis. Tumoroids were also prepared from CRC tumors resected from P2ry6+/+ mice to determine the role of P2Y6R in resistance to apoptosis, whereas HT29 carcinoma cells were used to elucidate the signaling mechanism involved in P2Y6R anti-apoptotic effect. P2ry6−/− mice developed a reduced number of colorectal tumors with apparent tumors having smaller volumes. Overall dysplastic score was significantly lower in P2ry6−/− animals. Stimulation of P2Y6R with the selective agonist MRS2693 protected HT-29 cells from TNFα-induced apoptosis. This protective effect was mediated by the stabilizing phosphorylation of the X-linked inhibitor of apoptosis protein (XIAP) by AKT. Using CRC-derived tumoroids, P2Y6R activation was found to contribute to chemoresistance since addition of the P2Y6R agonist MRS2693 significantly prevented the cytotoxic effect of 5-fluorouracil. The present study shows that sustained activation of P2Y6R may contribute to intestinal tumorigenesis by blocking the apoptotic process and by contributing to chemoresistance, a substantial concern in the treatment of patients with CRC. These results suggest that P2Y6R may represent a prime target for reducing colorectal carcinogenesis.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Towards a Multi-Pixel Photon-to-Digital Converter for Time-Bin Quantum Key Distribution

We present an integrated single-photon detection device custom designed for quantum key distribution (QKD) with time-bin encoded single photons. We implemented and demonstrated a prototype photon-to-digital converter (PDC) that integrates an 8 × 8 single-photon avalanche diode (SPAD) array with on-chip digital signal processing built in TSMC 65 nm CMOS. The prototype SPADs are used to validate the QKD functionalities with an array of time-to-digital converters (TDCs) to timestamp and process the photon detection events. The PDC uses window gating to reject noise counts and on-chip processing to sort the photon detections into respective time-bins. The PDC prototype achieved a 22.7 ps RMS timing resolution and demonstrated operation in a time-bin setup with 158 ps time-bins at an optical wavelength of 410 nm. This PDC can therefore be an important building block for a QKD receiver and enables compact and robust time-bin QKD systems with imaging detectors