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Metabolic interactions between multiple cell types are difficult to model using existing approaches. Here we present a workflow that integrates gene expression data, proteomics data and literature-based manual curation to model human metabolism within and between different types of cells. Transport reactions are used to account for the transfer of(More)
Measuring the causal effects of online advertising (adfx) on user behavior is important to the health of the WWW publishing industry. In this paper, using three controlled experiments, we show that observational data frequently lead to incorrect estimates of adfx. The reason, which we label "activity bias," comes from the surprising amount of time-based(More)
We know little about the dynamic economic impacts of natural disasters. I examine the effect of hurricanes on US counties' economies 0-10 years after landfall. Overall, I nd no substantial changes in county population, earnings, or the employment rate. The largest empirical effect of a hurricane is observed in large increases in government transfer payments(More)
A growing literature studies social networks and their implications for economic outcomes. This paper highlights, examines, and addresses econometric problems that arise when a researcher studies these network effects using sampled network data. In applied work, researchers generally construct networks from data collected from a partial sample of nodes. For(More)
We measure the causal effects of online advertising on sales, using a randomized experiment performed in cooperation between Yahoo! and a major retailer. After identifying over one million customers matched in the databases of the retailer and Yahoo!, we randomly assign them to treatment and control groups. We analyze individual-level data on ad exposure(More)
"North" ads, or sponsored listings appearing just above the organic search results, generate the majority of clicks and revenues for search engines. In this paper, we ask whether the competing north ads exert externalities on each other. In particular, does increasing the number of rival north ads decrease the number of clicks I receive on my own north ad?(More)
We study the impact of display advertising on user search behavior using a field experiment. In such an experiment, the treatment group users are exposed to some display advertising campaign, while the control group users are not. During the campaign and the post-campaign period we monitor the user search queries and we label them as relevant or irrelevant(More)
Online consumer data presents new opportunities for measuring the effects of advertising. We combine search query data with the television commercial schedule for the 2011 Super Bowl to measure the causal impact of TV advertising on consumer search behavior. Examining 46 Super Bowl commercials, we generally find large spikes in search behavior related to(More)
Classical theories of the firm assume access to reliable signals to measure the causal impact of choice variables on profit. For advertising expenditure we show, using twenty-five online field experiments (representing $2.8 million) with major U.S. retailers and brokerages, that this assumption typically does not hold. Statistical evidence from the(More)
for generously providing the laboratory, Ze Yu for coordinating the use of laboratory, and Yuqi Zheng for excellent research assistance. All errors are our own. Abstract We study how gradualism-increasing required levels (" thresholds ") of contributions slowly over time rather than requiring a high level of contribution immediately-affects individuals'(More)