Dynamic competition with network externalities: why history matters

We consider dynamic competition among platforms in a market with network externalities. A platform that dominated the market in the previous period be- comes \focal" in the current period, in that agents play the equilibrium in which they join the focal platform whenever such equilibrium exists. Yet when faced with higher-quality competition, can a low-quality platform remain focal? In the nite-horizon case, the unique equilibrium is ecient for \patient" platforms; with an innite time horizon, however, there are multiple equilibria where ei- ther the low- or high-quality platform dominates. If qualities are stochastic, the platform with a better average quality wins with a higher probability, even when its realized quality is lower, and this probability increases as platforms become more patient. Hence social welfare may decline as platforms become more forward looking

Dynamic competition with network externalities: why history matters

We consider dynamic competition among platforms in a market with network externalities. A platform that dominated the market in the previous period be- comes \focal" in the current period, in that agents play the equilibrium in which they join the focal platform whenever such equilibrium exists. Yet when faced with higher-quality competition, can a low-quality platform remain focal? In the nite-horizon case, the unique equilibrium is ecient for \patient" platforms; with an innite time horizon, however, there are multiple equilibria where ei- ther the low- or high-quality platform dominates. If qualities are stochastic, the platform with a better average quality wins with a higher probability, even when its realized quality is lower, and this probability increases as platforms become more patient. Hence social welfare may decline as platforms become more forward looking

Effect of the COVID-19 Pandemic on Patient Volumes, Acuity, and Outcomes in Pediatric Emergency Departments: A Nationwide Study

Objectives The aim of this study was to quantify the effect of the COVID-19 pandemic on pediatric emergency department (ED) utilization and outcomes. Methods This study is an interrupted-Time-series observational study of children presenting to 11 Canadian tertiary-care pediatric EDs. Data were grouped into weeks in 3 study periods: prepandemic (January 1, 2018-January 27, 2020), peripandemic (January 28, 2020-March 10, 2020), and early pandemic (March 11, 2020-April 30, 2020). These periods were compared with the same time intervals in the 2 preceding calendar years. Primary outcomes were number of ED visits per week. The secondary outcomes were triage acuity, hospitalization, intensive care unit (ICU) admission, mortality, length of hospital stay, ED revisits, and visits for trauma and mental health concerns. Results There were 577,807 ED visits (median age, 4.5 years; 52.9% male). Relative to the prepandemic period, there was a reduction [-58%; 95% confidence interval (CI),-63% to-51%] in the number of ED visits during the early-pandemic period, with concomitant higher acuity. There was a concurrent increase in the proportion of ward [odds ratio (OR), 1.39; 95% CI, 1.32-1.45] and intensive care unit (OR, 1.20; 95% CI, 1.01-1.42) admissions, and trauma-related ED visits among children less than 10 years (OR, 1.51; 95% CI, 1.45-1.56). Mental health-related visits in children declined in the early-pandemic period (in \u3c10 years,-60%; 95% CI,-67% to-51%; in children ≥10 years:-56%; 95% CI,-63% to-47%) relative to the pre-COVID-19 period. There were no differences in mortality or length of stay; however, ED revisits within 72 hours were reduced during the early-pandemic period (percent change:-55%; 95% CI,-61% to-49%; P \u3c 0.001). Conclusions After the declaration of the COVID-19 pandemic, dramatic reductions in pediatric ED visits occurred across Canada. Children seeking ED care were sicker, and there was an increase in trauma-related visits among children more than 10 years of age, whereas mental health visits declined during the early-pandemic period. When faced with a future pandemic, public health officials must consider the impact of the illness and the measures implemented on children\u27s health and acute care needs

Arabic and contact-induced change

This volume offers a synthesis of current expertise on contact-induced change in Arabic and its neighbours, with thirty chapters written by many of the leading experts on this topic. Its purpose is to showcase the current state of knowledge regarding the diverse outcomes of contacts between Arabic and other languages, in a format that is both accessible and useful to Arabists, historical linguists, and students of language contact

Arabic and contact-induced change

This volume offers a synthesis of current expertise on contact-induced change in Arabic and its neighbours, with thirty chapters written by many of the leading experts on this topic. Its purpose is to showcase the current state of knowledge regarding the diverse outcomes of contacts between Arabic and other languages, in a format that is both accessible and useful to Arabists, historical linguists, and students of language contact

Arabic and contact-induced change

This volume offers a synthesis of current expertise on contact-induced change in Arabic and its neighbours, with thirty chapters written by many of the leading experts on this topic. Its purpose is to showcase the current state of knowledge regarding the diverse outcomes of contacts between Arabic and other languages, in a format that is both accessible and useful to Arabists, historical linguists, and students of language contact

Arabic and contact-induced change

This volume offers a synthesis of current expertise on contact-induced change in Arabic and its neighbours, with thirty chapters written by many of the leading experts on this topic. Its purpose is to showcase the current state of knowledge regarding the diverse outcomes of contacts between Arabic and other languages, in a format that is both accessible and useful to Arabists, historical linguists, and students of language contact

Arabic and contact-induced change

This volume offers a synthesis of current expertise on contact-induced change in Arabic and its neighbours, with thirty chapters written by many of the leading experts on this topic. Its purpose is to showcase the current state of knowledge regarding the diverse outcomes of contacts between Arabic and other languages, in a format that is both accessible and useful to Arabists, historical linguists, and students of language contact

Arabic and contact-induced change

This volume offers a synthesis of current expertise on contact-induced change in Arabic and its neighbours, with thirty chapters written by many of the leading experts on this topic. Its purpose is to showcase the current state of knowledge regarding the diverse outcomes of contacts between Arabic and other languages, in a format that is both accessible and useful to Arabists, historical linguists, and students of language contact

Arabic and contact-induced change

This volume offers a synthesis of current expertise on contact-induced change in Arabic and its neighbours, with thirty chapters written by many of the leading experts on this topic. Its purpose is to showcase the current state of knowledge regarding the diverse outcomes of contacts between Arabic and other languages, in a format that is both accessible and useful to Arabists, historical linguists, and students of language contact