The spatial structure of networks

We study networks that connect points in geographic space, such as transportation networks and the Internet. We find that there are strong signatures in these networks of topography and use patterns, giving the networks shapes that are quite distinct from one another and from non-geographic networks. We offer an explanation of these differences in terms of the costs and benefits of transportation and communication, and give a simple model based on the Monte Carlo optimization of these costs and benefits that reproduces well the qualitative features of the networks studied.Comment: 5 pages, 3 figure

Optimal design of spatial distribution networks

We consider the problem of constructing public facilities, such as hospitals, airports, or malls, in a country with a non-uniform population density, such that the average distance from a person's home to the nearest facility is minimized. Approximate analytic arguments suggest that the optimal distribution of facilities should have a density that increases with population density, but does so slower than linearly, as the two-thirds power. This result is confirmed numerically for the particular case of the United States with recent population data using two independent methods, one a straightforward regression analysis, the other based on density dependent map projections. We also consider strategies for linking the facilities to form a spatial network, such as a network of flights between airports, so that the combined cost of maintenance of and travel on the network is minimized. We show specific examples of such optimal networks for the case of the United States.Comment: 6 pages, 5 figure

Reply to Comment on "Chiral suppression of scalar glueball decay"

Reply to the comment of Chao, He, and Ma

DIRECT PRODUCT PROFIT: A VIEW FROM THE SUPERMARKET INDUSTRY

Direct Product Profit (DPP) is a decision making tool that helps the food merchandiser by providing a better indication of the profitability of products on the supermarket shelves. Direct Product Profit allocates Direct Product Costs (DPC) to individual products. These DPCs are subtracted from gross margin to derive DPP. This paper reports on the use of DPP in the syrup product section of a chain of supermarkets. Implications for managerial action are also discussed.Agribusiness,

Not your father's oil shock

Factors other than changes in oil supply may cause changes in oil prices.Petroleum products - Prices

Whatever happened to the business cycle? a Bayesian analysis of jobless recoveries

During the typical recovery from U.S. post-War period economic downturns, employment recovers to its pre-recession level within months of the output trough. However, during the last two recoveries, employment has taken up to two years to achieve its pre-recession benchmark. We propose a formal empirical model of business cycles with recovery periods to demonstrate that the last two recoveries have been statistically different from previous experiences. We find that this difference can be attributed to a shift in the speed of transition between business cycle regimes. Moreover, we find this shift results from both durable and non-durable manufacturing sectors losing their cyclical characteristics. We argue that this finding of acyclicality in post-1980 manufacturing sectors is consistent with previous hypotheses (e.g., improved inventory management) regarding the reduction in macroeconomic volatility over the same period. These results suggest a link between the two phenomena, which have heretofore been studied separately.Business cycles ; Labor market

Can a summer hike cause a surprise fall for mortgage rates?

Federal funds rate ; Mortgages ; Interest rates

Look who's still working now

Labor supply ; Retirement ; Labor market