"The Financial Requirements of Achieving Gender Equality and Women's Empowerment"

Although the Millennium Development Goals (MDGs) have been ratified in global and national forums, they have not yet been incorporated into operational planning within governments or international organizations. The weak link between the policies and the investments needed for their implementation is one barrier to progress. An assessment of the resources required is a critical first step in formulating and implementing strategies to achieve the MDGs. This is especially true for policies to promote gender equality and empower women. Although enough is known about such policies to implement them successfully, the costs of such interventions are not systematically calculated and integrated into country-level budgeting processes. Using country-level data, the paper estimates the costs of interventions aimed at promoting gender equality and women's empowerment in Bangladesh, Cambodia, Ghana, Tanzania, and Uganda. It then uses these estimates to calculate the costs of such interventions in other low-income countries. Finally, the paper projects the financing gap for interventions that aim directly at achieving gender equality, first for the five countries, and subsequently for all low-income countries.

Goods Prices and Availability in Cities

This paper uses detailed barcode data on purchase transactions by households in 49 U.S. cities to calculate the first theoretically-founded urban price index. In doing so, we overcome a large number of problems that have plagued spatial price index measurement. We identify two important sources of bias. Heterogeneity bias arises from comparing different goods in different locations, and variety bias arises from not correcting for the fact that some goods are unavailable in some locations. Eliminating heterogeneity bias causes 97 percent of the variance in the price level of food products across cities to disappear relative to a conventional index. Eliminating both biases reverses the common finding that prices tend to be higher in larger cities. Instead, we find that price level for food products falls with city size

Goods Prices and Availability in Cities

This paper uses detailed barcode data on purchase transactions by households in 49 U.S. cities to overcome a large number of problems that have plagued spatial price index measurement. We identify two important sources of bias. Heterogeneity bias arises from comparing different goods in different locations, and variety bias arises from not correcting for the fact that some goods are unavailable in some locations. Eliminating heterogeneity bias causes 97 percent of the variance in the price level of food products across cities to disappear relative to a conventional index. Eliminating both biases reverses the common finding that prices tend to be higher in larger cities. Instead, we find that price level for food products falls with city size.

Essays on Prices and Variety Across Cities

In Krugman (1991), agglomeration is driven by consumption externalities related to differences in the average price across locations. Variety plays a central role here: the price index is lower in larger cities because more varieties are produced there, but all products are available everywhere, so there are no direct consumption gains from variety. Chapter 1 extends this model to allow for these variety differences across cities via an extensive margin of intercity trade. In this model, scale economies yield more production variety in larger cities so that, with positive trade costs, consumers in these locations can benefit from two consumption advantages - lower average prices and more varieties of products. This model sets the stage for the empirical chapters that measure the impact of these consumption benefits on consumer utility. The urban economics literature has paid relatively little attention to these consumption externalities for two reasons. First, the fact that wages are higher in larger cities indicates, in the context of a spatial equilibrium model, that purchasing power must be lower in these locations, which is inconsistent with the NEG theoretical predictions that price indexes are lower in larger cities. Second, there are reasons to believe that intranational trade frictions are much smaller than those across international borders. While there is a large body of work documenting that these frictions yield significant variation in the prices charged and varieties offered across different countries, we know relatively little about the spatial variation of price and variety in a domestic context. Chapter 2, co-authored with David E. Weinstein, addresses both of these issues. We first show that, controlling for purchaser demographics and store amenities, the prices of tradable products do, in fact, vary across cities as predicted by Krugman (1991). Additionally, we find that there are significant differences in the variety of products offered in large as opposed to small cities. We finally measure the extent to which this variation in prices and variety lowers price indexes for tradable products in large cities relative to small cities. This low price index over tradables in large cities is consistent with nominal wages being higher there, as long as there are congestion costs that equalize real income across locations. A major assumption in the work described above is that the consumption benefits of cities do not vary systematically across consumer types. The final chapter of my dissertation considers how systematic differences in prices and variety across space might impact different individuals differently. Previous research has tested whether firms vary prices and product offerings in order to cater local tastes in a market. I extend this analysis to structurally estimate how this behavior of individual firms differentially affects the price indexes faced by consumers with systematically heterogeneous tastes. I allow for tastes to vary with income and find that poor consumers face lower costs in low-income cities, while the opposite holds for wealthy consumers, whose tastes are better-suited to the variety of products available in high-income cities. In conclusion, this dissertation finds that there is significant variation in prices and variety across U.S. cities. In particular, the spatial distributions of prices, variety, and consumers in the U.S. are correlated in a manner consistent with there being consumption externalities. Consumers in larger cities have access to more varieties of products at a lower average price and, conditional on city size, consumers have access to varieties better-suited to the tastes of they share with their income group in cities with per capita incomes closer to their own. These patterns are reflected in the variation in the tradables price indexes that consumers face across large and small and across wealthy and poor cities. This evidence on the existence of the pecuniary consumption externalities hypothesized in early NEG papers supports a growing literature exploring the role of consmption externalities in generating the aggregate and skill-biased agglomeration patterns that the more recent NEG literature associates with production externalities

Measuring Movement and Social Contact with Smartphone Data: A Real-time Application to COVID-19

Tracking human activity in real time and at fine spatial scale is particularly valuable during episodes such as the COVID-19 pandemic. In this paper, we discuss the suitability of smartphone data for quantifying movement and social contact. We show that these data cover broad sections of the US population and exhibit movement patterns similar to conventional survey data. We develop and make publicly available a location exposure index that summarizes county-to-county movements and a device exposure index that quantifies social contact within venues. We use these indices to document how pandemic-induced reductions in activity vary across people and places

Formation of terrestrial planet cores inside giant planet embryos

Giant planet embryos are believed to be spawned by gravitational instability in massive extended (R ~ 100 AU) protostellar discs. In a recent paper we have shown that dust can sediment inside the embryos, as argued earlier by Boss (1998) in a slightly different model. Here we study numerically the next stage of this process -- the formation of a solid core. If conditions are conducive to solid core formation, the centre of the gas cloud goes through the following sequence of phases: (i) becomes grain (and metal) rich; (ii) forms a terrestrial mass solid core via a rapid collapse driven by self-gravity of the grains; (iii) starts to accrete a gaseous atmosphere when the solid core reaches mass of a few to 10 Earth masses. This sequence of events may build either terrestrial planet cores or metal rich giant planets inside the larger gas reservoir of the giant planet embryo. In a companion Letter we argue that tidal and irradiation effects from the parent star should disrupt the outer metal poor layers of the embryo, releasing nearly "ready to use" planets. We propose this as an alternative way to build planets.Comment: 20 pages, submitted to MNRAS, referred to as "paper II" in serie

A numerical simulation of a "super-Earth" core delivery from ~ 100 AU to ~ 8 AU

We use SPH simulations with an approximate radiative cooling prescription to model evolution of a massive and large ($\sim 100$ AU) very young protoplanetary disc. We also model dust growth and gas-grain dynamics with a second fluid approach. It is found that the disc fragments onto a large number of $\sim 10$ Jupiter mass clumps that cool and contract slowly. Some of the clumps evolve onto eccentric orbits delivering them into the inner tens of AU, where they are disrupted by tidal forces from the star. Dust grows and sediments inside the clumps, displaying a very strong segregation, with the largest particles forming dense cores in the centres. The density of the dust cores may exceed that of the gas and is limited only by the numerical constraints, indicating that these cores should collapse into rocky planetary cores. One particular giant planet embryo migrates inward close enough to be disrupted at about 10 AU, leaving a self-bound solid core of about 7.5 \mearth mass on a low eccentricity orbit at a radius of $\sim$ 8 AU. These simulations support the recent suggestions that terrestrial and giant planets may be the remnants of tidally disrupted giant planet embryos.Comment: Accepted by MNRAS. Animations of the simulation are available at http://www.astro.le.ac.uk/~shc14/Movie

Dispersal of protoplanetary disks by central wind stripping

We present a model for the dispersal of protoplanetary disks by winds from either the central star or the inner disk. These winds obliquely strike the flaring disk surface and strip away disk material by entraining it in an outward radial-moving flow at the wind-disk interface which lies several disk scale heights above the mid-plane. The disk dispersal time depends on the entrainment velocity at which disk material flows into this turbulent shear layer interface. If the entrainment efficiency is ~10% of the local sound speed, a likely upper limit, the dispersal time at 1 AU is ~6 Myr for a disk with a surface density of 10^3 g cm^{-2}, a solar mass central star, and a wind with an outflow rate 10^{-8} Msun/yr and terminal velocity 200 km/s. When compared to photoevaporation and viscous evolution, wind stripping can be a dominant mechanism only for the combination of low accretion rates (< 10^{-8} Msun/yr) and wind outflow rates approaching these accretion rates. This case is unusual since generally outflow rates are < 0.1 of of accretion rates.Comment: 12 pages, 9 figures, accepted for publication in Ap

Simulations of spiral galaxies with an active potential: molecular cloud formation and gas dynamics

We describe simulations of the response of a gaseous disc to an active spiral potential. The potential is derived from an N-body calculation and leads to a multi-armed time-evolving pattern. The gas forms long spiral arms typical of grand design galaxies, although the spiral pattern is asymmetric. The primary difference from a grand-design spiral galaxy, which has a consistent 2/4-armed pattern, is that instead of passing through the spiral arms, gas generally falls into a developing potential minimum and is released only when the local minimum dissolves. In this case, the densest gas is coincident with the spiral potential, rather than offset as in the grand-design spirals. We would there fore expect no offset between the spiral shock and star formation, and no obvious co-rotation radius. Spurs which occur in grand-design spirals when large clumps are sheared off leaving the spiral arms, are rare in the active, time-evolving spiral reported here. Instead, large branches are formed from spiral arms when the underlying spiral potential is dissolving due to the N-body dynamics. We find that the molecular cloud mass spectrum for the active potential is similar to that for clouds in grand design calculations, depending primarily on the ambient pressure rather than the nature of the potential. The largest molecular clouds occur when spiral arms collide, rather than by agglomeration within a spiral arm.Comment: 11 pages, 7 figures, accepted for publication in MNRA

The Empirics of Agglomeration Economies

We propose an integrated framework to discuss the empirical literature on the local determinants of agglomeration effects. We start by presenting the theoretical mechanisms that ground individual and aggregate empirical specifications. We gradually introduce static effects, dynamic effects, and workers' endogenous location choices. We emphasise the impact of local density on productivity but we also consider many other local determinants supported by theory. Empirical issues are then addressed. Most important concerns are about endogeneity at the local and individual levels, the choice of a productivity measure between wage and TFP, and the roles of spatial scale, firms' characteristics, and functional forms. Estimated impacts of local determinants of productivity, employment, and firms' locations choices are surveyed for both developed and developing economies. We finally provide a discussion of attempts to identify and quantify specific agglomeration mechanisms