Tanguy Brachet

The Effect of Shift Structure on Performance

Tanguy Brachet et al. — Fri, 27 Nov 2009 22:36:34 PST

The effect of shift structure on worker performance and productivity is of increasing interest to firms and regulatory bodies. Using approximately 743,000 emergency medical incidents attended by 2,381 paramedics in Mississippi, we evaluate the extent that paramedics’ performance towards the end of shifts is impacted by shift length. We find evidence that performance deteriorates towards the end of long shifts, and argue that fatigue is the mediating factor. Our calculations imply that such deterioration may result in a 0.76% increase in 30-day mortality. These findings have implications for workforce organization, calling attention to regulation designed to limit extended work hours.

The Hospital Compare Mortality Model and the Volume–Outcome Relationship

Jeffrey H. Silber et al. — Fri, 27 Nov 2009 22:12:55 PST

Objective: We ask whether Medicare's Hospital Compare random effects model correctly assesses acute myocardial infarction (AMI) hospital mortality rates when there is a volume–outcome relationship.

Data Sources/Study Setting: Medicare claims on 208,157 AMI patients admitted in 3,629 acute care hospitals throughout the United States.

Study Design: We compared average-adjusted mortality using logistic regression with average adjusted mortality based on the Hospital Compare random effects model. We then fit random effects models with the same patient variables as in Medicare's Hospital Compare mortality model but also included terms for hospital Medicare AMI volume and another model that additionally included other hospital characteristics.

Principal Findings: Hospital Compare's average adjusted mortality significantly underestimates average observed death rates in small volume hospitals. Placing hospital volume in the Hospital Compare model significantly improved predictions.

Conclusions: The Hospital Compare random effects model underestimates the typically poorer performance of low-volume hospitals. Placing hospital volume in the Hospital Compare model, and possibly other important hospital characteristics, appears indicated when using a random effects model to predict outcomes. Care must be taken to insure the proper method of reporting such models, especially if hospital characteristics are included in the random effects model.

The Time Cost of Prehospital Intubation and Intravenous Access in Trauma Patients

Brendan G. Carr et al. — Wed, 04 Feb 2009 20:38:04 PST

Objectives. The prehospital management of trauma patients remains controversial. Little is known about the time each procedure contributes to the on-scene duration, and this information would be helpful in prioritizing which procedures to perform in the prehospital setting. We sought to estimate the contribution of procedures to on-scene duration focusing on intubation and establishment of intravenous (IV) access.

Methods. Data were provided by the Office of Emergency Planning and Response at the Mississippi Department of Health. Real-time prehospital patient-level data are collected by emergency medical services (EMS) providers for all 9-1-1 calls statewide. Linear regression was performed to determine the overall additional time for an average procedure and to calculate marginal increases in on-scene time associated with the establishment of IV access and with endotracheal intubation. Analyses were performed using Stata 9.

Results. During 2001–2005, 192,055 prehospital runs were made for trauma patients. 121,495 (63%) included prehospital procedures. Average on-scene duration for those runs was 15:24 (minutes:seconds). On average, each procedure was associated with an addition of 1 minute to the on-scene duration (95% confidence interval [CI]: 58–62 seconds). A scene involving the establishment of IV access was 5:04 longer, while one involving tracheal intubation was 2:36 longer.

Conclusions. We estimate the marginal increase in on-scene duration associated with the performance of an average procedure, establishment of IV access, and endotracheal intubation. There are policy and planning implications for the time trade-off of prehospital procedures, especially discretionary ones.

Press coverage: http://www.jems.com/article/cardiac-circulation/how-much-do-ems-procedures-cos-0

Economies of Scale

Tanguy Brachet et al. — Wed, 04 Feb 2009 20:25:27 PST

On The Determinants of Organizational Forgetting

Tanguy Brachet et al. — Wed, 04 Feb 2009 14:57:44 PST

Studies of organizational learning and forgetting identify potential channels through which the firm’s production experience is lost. While the ability to distinguish between these channels has implications for efficient resource allocation within the firm, to date, their relative importance has been ignored. This paper develops a framework for eliciting the contributions of labor turnover and human capital depreciation to organizational forgetting. We apply our framework to a novel dataset of ambulance companies and their workforce. We find evidence of organizational forgetting, which results from sizable skill decay and turnover effects, with the latter having twice the magnitude of the former. (http://www.aeaweb.org/articles.php?doi=10.1257/mic.3.3.100)

Retention, Learning-by-Doing, and Performance in Emergency Medical Services

Guy David et al. — Mon, 02 Feb 2009 22:57:01 PST

Objectives. To examine the strength of the volume–outcome relationship among paramedics, a group of providers that has not been previously studied in this context. By identifying the effects of individual learning on performance, we also assess the value of paramedics' retention. The prehospital emergency medical services (EMS) setting allows us to interpret any volume–outcome relationship as learning by doing, uncontaminated by reputation-based referrals because ambulance units are dispatched based on proximity.

Data Sources. Incident-level EMS data spanning 1991 to 2005 from the Mississippi Emergency Medical Services Information System collected by the Mississippi Department of Health.

Research Design. Using linear and quantile methods with and without provider fixed effects, we estimate the relationship between experience accumulation and performance using the universe of trauma incidents involving injured patients (including motor vehicle crashes, falls, stabbings, and shootings).

Principal Findings. We find that greater individual volume is robustly related to improved performance. In addition, we find that the benefit of learning operates through both recent and past experiences, accrues differentially across tenure groups, and operates on both mean performance and the upper quantiles of the performance distribution.

Conclusions. Persistent past and current volume effects suggest that policy and managerial implications in EMS should be directed at retention efforts to take advantage of individual learning by paramedics.

Computing Clustered Standard Errors for Two-Stage Least Squares in SAS

Tanguy Brachet — Thu, 12 Apr 2007 10:30:40 PDT

Since SAS doesn't offer a 2SLS procedure that allows for clustered standard errors, this macro develops an equivalent algorithm based on SAS's available procedures. The steps are as follows: [1] estimate the first stage by OLS and save the endogenous variable's predicted values (PROC REG); [2] estimate the structural equation as usual and save the 2SLS residuals (PROC SYSLIN); [3] merge the dataset containing the first stage predictions with that containing the 2SLS residuals; [4] regress the 2SLS residuals on the 1st stage predicted values and all other exogenous variables, clustering the standard errors by the cluster variable (PROC SURVEYREG). The standard errors reported in step [4] are the clustered 2SLS standard errors.

Maternal Smoking, Misclassification, and Infant Health

Tanguy Brachet — Sat, 25 Nov 2006 22:50:59 PST

Identifying the causal effect of prenatal maternal smoking on infant health is complicated by unobservable maternal characteristics and behaviors which are plausibly related to both birth outcomes and a mother’s propensity to smoke. Previous studies have addressed the omitted variables problem using instrumental variables (IV) techniques. However, with self-reported data on maternal smoking, misreporting can induce more severe biases in IV estimates than in OLS. This paper proposes an approach based on parametric methods for misclassified binary dependent variables that simultaneously addresses the endogeneity and measurement error problems. The relationship between infant health and maternal smoking is then re-examined using US Birth Records. I find that roughly 30% of smoking mothers are misclassified as non-smokers. As a result, conventional IV estimates deliver implausibly large birth weight losses (upwards of 1,000 grams among African Americans). Accounting for misclassification yields estimates that are considerably smaller in magnitude and more consistent with experimental evidence.