This paper introduces a stata implementation of coarsened exact matching. Two roads diverged in a narrow datasetwhen coarsened exact. Thus each member is given a bin signature that will be used to exactly match other. The stata blog exact matching on discrete covariates is the. In this paper we introduce %cem, a macro package allowing researchers to automatically perform coarsened exact matching cem in sas environment. This function transforms a typical cem matching solution to a ktok match, with k variable along strata. One approach to impact evaluation is the use of coarsened exact matching, a statistical technique that allows researchers to compare program participants to nonparticipants, controlling for factors believed to influence outcomes of interest. Collapsing categories or cutting up discrete covariates performs the same function as a bandwidth in nonparametric kernel regression.
This option will delete some data that matched well, and thus likely increase the variance, but it means that subsequent. We address the possibility of unobserved selfselection into exit mode by using coarsened exact matching, and in two additional ways. The program implements the coarsened exact matching cem. Nearest neighbor, radius, coarsened exact, percentile rank and mahalanobis and euclidean distance matching. Cem is a nonparametric matching method widely used by researchers to avoid the confounding influence of pretreatment control variables to improve causal inference in quasiexperimental studies. Coarsened exact matching is faster, is easier to use and understand, requires fewer assumptions, is more easily automated, and possesses more attractive statistical properties for many applications than do existing matching methods. This option will delete some data that matched well, and thus likely increase the variance, but it means that subsequent analyses do not require weights. In this article, we introduce a stata implementation of coarsened exact matching, a new method for improving the estimation of causal effects by. The most common matching technique, propensity score matching, however, is slow and difficult to apply. The cem command implements the coarsened exact matching algorithm in stata. Once all five are downloaded, users can generate the following.
Causal effect of selfesteem on cigarette smoking stages. Matthew blackwell harvard university stefano iacus university of milan gary king harvard university giuseppe porro university of trieste. Exact matching dear statalist members, i am trying to run a coarsened exact matching to create comparable pair of individuals within my sample. Coarsened exact matching in stata matthew blackwell. Another alternative is the coarsened exact matching procedure of blackwell et al. In coarsened exact matching, users temporarily coarsen their data, exact match on these coarsened data, and then. Matthew blackwell, stefano iacus, gary king and giuseppe porro additional contact information matthew blackwell. Coarsened exact matching explained devmotivation medium. This paper introduces a stata implementation of coarsened exact matching cem, a. The cem package provides a stata implementation of coarsened exact matching, a new method for improving the estimation of causal effects by reducing imbalance in covariates between. Aug 16, 2016 exact matching on discrete covariates and ra with fully interacted discrete covariates perform the same nonparametric estimation.
We started with the procedure of coarsened exact matching to identify poes that more closely resemble the soes in the database both. It implements an efficient method for distance based matching preventing the inflationary increment of the runtime. Coarsened exact matching coarsened exact matching cem is a monotonoic imbalance bounding mib matching method which means that the balance between the treated and control groups is chosen by the user ex ante rather than discovered through the usual laborious process of checking after the fact and repeatedly reestimating, and so that adjusting the imbalance on one variable has no effect. Coarsened exact matching coarsened exact matching cem is a monotonoic imbalance bounding mib matching method which means that the balance between the treated and control groups is chosen by the user ex ante rather than discovered through the usual laborious process of checking after the fact and repeatedly reestimating, and so that. Coarsened exact matching cem is a relatively new causal inference technique that allows the researcher to nonparametrically create a matched dataset to evaluate the effect of a treatment. Coarsened exact matching is faster, is easier to use and understand, requires fewer assumptions. For instance, adding one continuous variable to a dataset e ectively kills exact matching since two observations. Other matching methods inheret many of cems properties when applied to.
In cem, users temporarily coarsen their data, exact match on these coarsened data, then run their analysis on the uncoarsened, matched data. Coarsened exact matching in stata gary king harvard. Coarsened exact matching in stata matthew blackwell1 stefano iacus2 gary king3 giuseppe porro4 february 22, 2010 1institute for quantitative social science,1737 cambridge street, harvard university, cam bridge ma 028. To enable construction of a survival curve, matching on age, gender, systolic bp, bmi, and smoking was done using coarsened exact matching. Download resource psi uses impact evaluation to determine if our programs are working. Using sas software to perform a casecontrol match on propensity score in an. We discuss a method for improving causal inferences called coarsened exact matching cem, and the new monotonic imbalance bounding mib class of matching methods from which cem is derived.
A member is represented by properties coarsened to discrete values using a coarsening or binning strategy. Propensity score matching psm is the older, more established technique in the literature. Coarsened exact matching cem package in stata statalist. Article pdf available in stata journal 98 january 2010 with 973 reads. Another approach you might consider is using coarsened exact matching, cem, a user written program found on ssc ssc install cem using. The cem package provides a stata implementation of coarsened exact matching, a new method for improving the estimation of causal effects by reducing imbalance in covariates between treated and control groups. Coarsened exact matching for stata matthew blackwell institute for quantitative social science harvard university joint work with stefano m. In this case, the algorithm outputs the same matching solution for each multiply imputed data set i. Abstract this paper introduces a stata implementation of coarsened exact matching cem, a new method for improving the estimation of causal effects by reducing imbalance in covariates between treated and control groups. Causal effect of selfesteem on cigarette smoking stages in.
Coarsened exact matching is faster, is easier to use and understand, requires fewer assumptions, is more easily automated, and. I have eliminated nas and am running matching on polity2 7 treatment. Coarsened exact matching in stata stata journal, 2009, with matthew blackwell, cem. Gary king of harvard university offers a different take on matching procedures by means of a new technique known as coarsened exact matching cem. Cem may be used alone or in combination with any existing matching method. Exact matching on discrete covariates and ra with fully interacted discrete covariates perform the same nonparametric estimation. Apr 19, 2017 a member is represented by properties coarsened to discrete values using a coarsening or binning strategy.
Download fulltext pdf download fulltext pdf download fulltext pdf download fulltext pdf. How to use cem for spss in order to demonstrate the syntax of cem in spss, you can download an example dataset of a job training program. My first step was to match the groups across a number of variables age, sex, preopasa, premob, and origin using the cem package for coarsened exact matching. The cem package provides a stata implementation of coarsened exact matching, a new method for improving the. Other matching methods inherit many of the coarsened exact matching methods properties when applied to further match data preprocessed by coarsened exact matching. This paper introduces a stata implementation of coarsened exact matching cem, a new method for improving the estimation of causal effects by reducing imbalance in covariates between treated and control groups. In this article, we introduce a stata implementation of coarsened exact matching, a new method for improving the estimation of causal effects by reducing imbalance in covariates between treated and control groups. I am trying to run coarsened exact matching on a dataset of 6549 observations and 94 variables. We summarize what is known about cem and mib, derive and illustrate several new desirable statistical. The program implements the coarsened exact matching cem algorithm described in.
Coarsened exact matching is faster, is easier to use and understand, requires fewer assumptions, is more easily automated, and possesses more attractive statistical. Ricardo, the first thing you would need to do is to generate a variable that indicates whether a firm was involved in an acquisition. Cem is faster, easier to use and understand, requires fewer assumptions, more easily automated, and possesses more attractive statistical properties for many applications than existing matching methods. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Iacus, gary king, and giuseppe porro, causal inference without balance checking. Cem via the dialog menu in order to demonstrate the syntax of cem in spss, you can download an example dataset of a job training program. Coarsened exact matching political analysis, 2012 and multivariate matching methods that are monotonic imbalance bounding jasa, 2011, cem. Exploring robust methods for evaluating treatment and. However when i come to running the command i am faced with the. Coarsened exact matching and multivariate matching methods that are monotonic imbalance bounding. The goal of the original study was to estimate the effect of a job training program the variable treated on real earnings in 1978 the variable re78.
This algorithm, and its statistical properties, are described in stefano m. Coarsened exact matching cem is a monotonoic imbalance bounding mib matching method which means that the balance between the treated and control groups is chosen by the user ex ante rather than discovered through the usual laborious process of checking after the fact and repeatedly reestimating, and so that adjusting the imbalance on one. Comparison of matching metrics and causal effects estimated from coarsened exact matching cem and propensity score matching psm effectiveness of two matching methodologies based on the qualitative and quantitative imbalance results observed in tables 1 and and2, 2, cem and psm were employed within the aforementioned sampling design. Students were matched based on coarsened exact matching on pretreatment variables, including age, gender, smoking stages at the first wave of study, socioeconomic status, general risktaking behavior, having a smoker in the family, having a smoker friend, attitude toward smoking, and selfinjury, to ensure statistically equivalent comparison.
Iacus and gary king and nathaniel beck and matt blackwell and andy eggers and adam glynn and justin grimmer and jens hainmueller and ben hansen and kosuke imai and guido imbens and fabrizia mealli, title causal inference without balance checking. Iacus, gary king, and giuseppe porro, matching for causal inference without balance checking. This paper introduces a stata implementation of coarsened exact matching cem, a new method for improving the estimation of causal effects by reducing imbalance in co. A coarsened exact matching approach this paper is the first to use the method of coarsened exact matching cem to estimate the impact of mood disorders on medical care costs in order to address the endogeneity of mood disorders. Hth david sent with verizon mobile email original message from. Statistical matching offers a solution to this problem by finding statistical twins, one with and one without the treatment. Reducing bias in a propensity score matchedpair sample using greedy matching techniques. Two roads diverged in a narrow datasetwhen coarsened. Coarsened exact matching cem on panel data statalist. The goal of the original study was to estimate the. Coarsened exact matching cem offers an alternative solution, which is faster and easier to understand. Harvard university statistical software components from boston college department of economics.
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