Propensity Score Matching Procedure Research Articles

Increased Risk of Acute Cholecystitis in Patients With Spinal Cord Injury

Retrospective cohort study. To evaluate the risk of acute cholecystitis (AC) in patients with spinal cord injury (SCI) based on a nationwide sample. Prior research evaluating the risk of AC in patients with SCI is limited. Moreover, since most previous studies on the association between AC and SCI used case-series designs, little is known about the relative risk of SCI patients developing AC from a longitudinal follow-up, compared with individuals without SCI. We used the data from Taiwan's National Health Insurance Research Database. The SCI group consisted of 11,523 patients with SCI aged between 20 and 90 years. Propensity score matching procedure was employed to minimize potential confounding effects arising from the imbalance in the baseline characteristics. A total of 23,046 propensity score-matched patients without SCI were enrolled in the non-SCI group. We compared the incidence of AC between these two groups, and assessed the impact of SCI on the risk of developing AC. In the SCI and non-SCI groups, the respective incidence rates of AC were 36.9 (95% confidence interval [CI], 30.0-44.8) and 25.2 (95% CI, 21.2-29.8) per 10,000 person-years. As compared with the non-SCI group, the hazard ratio for the SCI group of AC was 1.71 (95% CI, 1.22-2.41, P = 0.0018); and the cumulative incidence of AC of the SCI group was higher than that of the non-SCI group (P = 0.0036). This population-based cohort study showed that there was an increased risk of AC in patients with SCI. 3.

Cluster policy and firm performance: a case study of the French optic/photonic industry

ABSTRACTThis study analyzes the effects of a cluster policy on firms’ productivity, employment and total fixed assets in the French optic/photonic industry. Exploiting firm-level data between 1996 and 2008, it analyzes the selection process of the cluster policy through a logit model, before combining a propensity score matching (PSM) procedure and a difference-in-differences estimation to capture its impact on firms’ performance. It is shown that larger firms are more likely to be selected by the public policy. Second, the firms that received the competitiveness cluster certification became more productive and increased both their employment and their total fixed assets levels.

A study of long-lived asset impairment under U.S. GAAP and IFRS within the U.S. institutional environment

This paper explores whether differences in accounting standards influence reporting behavior within the U.S. institutional environment where both IFRS and U.S. GAAP are used for reporting purposes. We focus on the accounting for impairment of long-lived assets, an area where significant differences exist between U.S. GAAP and IFRS. We identify all U.S.-listed firms who have recognized long-lived asset impairment losses during the 2004–2012 period. From these firms, we identify firms following IFRS, then develop a matched sample of U.S. GAAP firms, using a propensity score matching procedure. We examine the relation between impairment loss and unexpectedly high or low earnings in the year of impairment using a two-stage Heckman regression model, controlling for industry, country, year of write-down, and firm-level economic factors. We find that the association between impairment losses and unexpectedly high and low earnings is significantly greater for U.S. GAAP firms as compared to IFRS reporting firms, implying differences in accounting standards influence firm financial reporting. Our findings are robust to alternative measures of country level institutional factors and macro-economic variables, as well as inclusion of asset impairment reversals.

Long-term oncological outcomes of local excision versus radical resection for early colorectal cancer in young patients without preoperative chemoradiotherapy: a population-based propensity matching study.

The incidence and mortality of colorectal carcinoma are rising in young adults. This population‐based propensity matching study aimed to compare long‐term oncological outcomes of local excision with radical resection for early localized colorectal cancer (CRC) in young patients without preoperative chemoradiotherapy. Patients under 45 years old with T1 colon or rectal adenocarcinoma who underwent local excision or radical resection were included from the Surveillance, Epidemiology, and End Results (SEER) database between 1998 and 2014. Survival curves were plotted using the Kaplan–Meier method. Cancer‐specific survival (CSS) was compared using adjusted hazard ratios (HRs) between local excision and radical resection. After propensity score matching procedure, total of 1719 patients were included in the analysis, among which 573 treated with local excision and 1146 treated with radical resection. The median follow‐up was 80 months (interquartile range(IQR): 37–132), with 1074 patients followed for ≥5 years and 508 patients followed for ≥10 years. Five‐year CSS of local excision versus radical resection was 93.4% versus 96.7% for colon cancer and 96.6% versus 98.4% for rectal cancer. Ten‐year CSS of local excision versus radical resection was 91.4% versus 94.0% for colon cancer and 92.8% versus 96.7% for rectal cancer. On multivariable analysis, compared with radical resection, local excision was not associated with inferior CSS for colon (HR 1.74, 95% CI: 0.92–3.29, P = 0.090) and rectal cancer (HR 2.16, 95% CI: 0.99–4.71, P = 0.052). There is no evidence of differential long‐term oncological outcomes between local excision and radical resection. These findings supported clinical application of local excision for early colon and rectal cancer in young adults.

Bus quality improvements and local commuter mode share

The choice to use bus transit over a rival mode of transportation is a consequence of many variables. The importance of bus service quality on mode share is often considered but rarely measured explicitly. This study presents a novel temporal data set of geolocated buses from New York City. The merger of locational vehicle data with public schedule data allows for the estimation of bus dependability across neighbourhoods. This study uses plausibly exogenous spatial variation in the introduction New York City’s Select Bus Service program to explore the relationship between the policy intervention, bus service quality and changes in commuter mode share. A propensity score matching procedure compares bus reliability and mode share in tracts that received Select Bus Service to a control group. A sizeable treatment effect is found. The policy intervention significantly increased service frequency and improved bus arrival reliability. Additionally, bus mode share amongst commuters in treatment neighbourhoods increased substantially. Select Bus Service was responsible for an increase in local bus mode share of 1.9 percentage points, with bus mode share in the median tract rising from 9.6% to 11.5%. Female commuters are found to be more responsive to the service improvements than males.

Comparison of efficacy of TNF inhibitors and abatacept in patients with rheumatoid arthritis; Adjusted with propensity score matching

The aim of this study was to compare the clinical outcome of patients with rheumatoid arthritis seen in routine clinical practice treated with either TNF inhibitors or abatacept. To overcome potential bias, both propensity score matching and Inverse Probability of Treatment Weighting were used for patient selection. The propensity score matching procedure selected 315 matched pairs of patients who were treated with TNF inhibitors or abatacept. At week 52, SDAI in TNF inhibitors was lower than abatacept. In contrast, analysis of biologics-naive patients using the propensity-score matching (n = 150; in each group) showed comparable clinical efficacy. Consistent results were obtained by the use of Inverse Probability of Treatment Weighting (581 patients treated with TNF inhibitors and 353 patients treated with abatacept). The predictors of response to each treatment were different; abatacept appeared to benefit patients with high baseline RF titers while TNF inhibitors appeared to benefit patients with low baseline HAQ-DI.

Monetizing Freemium Communities: Does Paying for Premium Increase Social Engagement?

Making sustainable profits from a baseline zero price and motivating free consumers to convert to premium subscribers is a continuing challenge for all freemium communities. Prior research has causally established that social engagement (Oestreicher-Singer and Zalmanson 2013) and peer influence (Bapna and Umyarov 2015) are two important drivers of users converting to premium subscribers in such communities. In this paper, we flip the perspective of prior research and ask whether the decision to pay for a premium subscription causes users to become more socially engaged. In the context of the Last.fm music listening freemium social community, we establish, using a novel 41-month-long panel dataset, a look-ahead propensity score matching (LA-PSM) procedure coupled with a difference-in-difference estimator of the treatment effect, that payment for premium leads to more social engagement. Specifically, we find that paying for premium leads to an increase in both content-related and community-related social engagement. Free users who convert to premium listen to 287.2% more songs, create 1.92% more playlists, exhibit a 2.01% increase in the number of forum posts made, and gain 15.77% more friends. Thus, premium subscribers create value not only for themselves by consuming more content, but also for the community and site by organizing more content and adding more friends, who are subsequently engaged by the social diffusion emerging from the focal user’s activities.

Monetizing Freemium Communities: Does Paying for Premium Increase Social Engagement?

Making sustainable profits from a baseline zero price and motivating free consumers to convert to premium subscribers is a continuing challenge for all freemium communities. Prior research has causally established that social engagement (Oestreicher-Singer and Zalmanson 2013) and peer influence (Bapna and Umyarov 2015) are two important drivers of users converting to premium subscribers in such communities. In this paper, we flip the perspective of prior research and ask whether the decision to pay for premium subscription causes users to become more socially engaged. In the context of the Last.fm music listening freemium social community, we establish, using a novel 41 month long panel dataset, a look-ahead propensity score matching (LA-PSM) procedure coupled with a difference-in-difference estimator of the treatment effect, that payment for premium leads to more social engagement. Specifically, we find that paying for premium leads to an increase in both content-related and community-related social engagement. Free users who convert to premium listen to 287.2% more songs, create 1.92% more playlists, exhibit a 2.01% increase in the number of forum posts made, and gain 15.77% more friends. Thus, premium subscribers create value not only for themselves by consuming more content, but also for the community and site by organizing more content and adding more friends, who are subsequently engaged by the social diffusion emerging from the focal user’s activities.

Adjusting for unmeasured spatial confounding with distance adjusted propensity score matching.

Propensity score matching is a common tool for adjusting for observed confounding in observational studies, but is known to have limitations in the presence of unmeasured confounding. In many settings, researchers are confronted with spatially-indexed data where the relative locations of the observational units may serve as a useful proxy for unmeasured confounding that varies according to a spatial pattern. We develop a new method, termed distance adjusted propensity score matching (DAPSm) that incorporates information on units' spatial proximity into a propensity score matching procedure. We show that DAPSm can adjust for both observed and some forms of unobserved confounding and evaluate its performance relative to several other reasonable alternatives for incorporating spatial information into propensity score adjustment. The method is motivated by and applied to a comparative effectiveness investigation of power plant emission reduction technologies designed to reduce population exposure to ambient ozone pollution. Ultimately, DAPSm provides a framework for augmenting a "standard" propensity score analysis with information on spatial proximity and provides a transparent and principled way to assess the relative trade-offs of prioritizing observed confounding adjustment versus spatial proximity adjustment.

Impact of Selective Aspiration Thrombectomy on Mortality in Patients With ST-Segment Elevation Myocardial Infarction

Although routine aspiration thrombectomy (AT) is not recommended by the current American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions guideline, for selected cases, a class IIb indication is given because of lack of data. We studied the impact of selective AT on mortality in patients with ST-segment elevation myocardial infarction using a prospective registry. We analyzed data of 1,255 patients, of whom 535 underwent AT based on operator's decision. Separate propensity score matching procedures were performed including all patients and only those with initial TIMI (Thrombolysis In Myocardial Infarction) 0 to 1 flow, indicating the highest thrombus burden. Primary outcome measure was time to all-cause death at 1 year. Both studies were sufficiently powered to detect the hazard ratio (HR) of 0.52 seen in the TAPAS (Thrombus Aspiration during Percutaneous coronary intervention in Acute myocardial infarction Study) trial. In the study with open inclusion criteria, 1-year mortality rates were 15.5% and 14.5% in the AT and conventional percutaneous coronary intervention arm, respectively (p = 0.77). The unadjusted HR was 1.05 (95% CI 0.73 to 1.51), p = 0.80, whereas the adjusted HR was 0.97 (95% CI 0.66 to 1.41), p = 0.87. In patients with initial TIMI 0 to 1 flow, mortality rate at 1 year was 15.6% in the AT and 16.7% in the standard percutaneous coronary intervention group (p = 0.76). The unadjusted and adjusted HRs were similar: 0.91 (95% CI 0.62 to 1.34), p = 0.65 and 0.93 (95% CI 0.62 to 1.37), p = 0.70, respectively. In conclusion, selective AT based on operator's discretion offers no mortality benefit of the magnitude detected in the TAPAS trial, even for patients with initial TIMI 0 to 1 flow grade.

Does the Use of Mobile Phones by Smallholder Maize Farmers Affect Productivity in Ghana?

ABSTRACTThis study evaluates the effects of mobile technology on productivity and the channels of transmission of these effects. Using propensity score matching procedures, the results show that mobile phone ownership and use significantly improves agricultural productivity. Specifically, the mobile phone improves the productivity of user-farmers by at least 261.20 kg/ha per production season. Further, we find that phone ownership and use impacts productivity more than phone use only. The identified channels of effect are extension services, adoption of modern technology and market participation. These results have key policy implications for Ghana and developing economies at large.

Impact of Farmers’ Training Centres on Household Income: Evidence from Propensity Score Matching in Eastern Ethiopia

In developing countries, agricultural advisory services (AASs) are regarded as a key component of economic development strategies in terms of improving productivity and livelihoods. Nevertheless, there is a dearth of empirical evidence on the impact of AASs in general and the Farmers’ Training Centres (FTCs) in particular. In this article, we employ the propensity score matching procedure to estimate the impact of an FTC-based training on household farm income in eastern Ethiopia. The result indicates a significant average gain of annual farm income by participants of the training, ranging from Birr 9557 to Birr 10,388 per household.

Interpersonal Communication in Response to an Intervention and Its Impact on Smoking Cessation Within a Low-Income Population.

It is a priority to develop population-based strategies for reducing barriers to smoking cessation among low-income populations. Harnessing secondary transmission such as interpersonal communication (IC) has helped to reduce tobacco use, but there is a dearth of quasi-experimental research that examines IC and the full spectrum of smoking cessation behaviors, particularly in the context of population-level programs. Using quasi-experimental methods, we examined IC in response to a population-level intervention and its impact on the full spectrum of smoking cessation outcomes among low-income smokers. We used propensity score matching; three different propensity score matching procedures were used to estimate and approximate experimental effects. We assessed four cessation outcomes: utilization of a free tobacco quitline (QL), making a quit attempt, and being smoke-free for 7 and 30 days at follow-up. We also examined predictors of IC. IC was significantly related to QL utilization (effect sizes ranging from 0.135 to 0.166), making a quit attempt (effect sizes ranging from 0.115 to 0.147), being smoke-free for 7 days (effect sizes ranging from 0.080 to 0.121), and being smoke-free for 30 days at follow-up (effect sizes ranging from 0.058 to 0.082). Program-related and participant characteristics predicted IC, such as receiving emotional direct mail materials and living with a fellow smoker. IC in response to a population-based program affected the cessation process, and IC had a marked impact on sustained cessation. Population-based programs should aim to harness psychosocial dynamics such as IC to promote sustained cessation among low-income populations.

Managerial foreign experience and corporate innovation

This study examines the impact of managerial foreign experience on corporate innovation using manually collected data of Chinese listed companies. We find that managerial foreign experience is positively associated with corporate innovation. This association is robust to a series of robustness checks, including the use of Heckman two-step sample selection model, propensity score matching procedure, and the market reaction to the appointing announcements of managers with foreign experience. Further analyses indicate that senior managers with foreign experience have a more significant impact on corporate innovation than junior managers with foreign experience; both foreign study experience and foreign work experience have important impacts on corporate innovation; managers with foreign experience in private enterprises have more initiatives to innovate than in state-owned enterprises; and managers who gain foreign experience in the United States tend to be more influential and innovative than those who have foreign experience from other countries or regions. Overall, our results suggest that managerial foreign experience matters for corporate innovation in emerging markets.

Effect of Influenza Vaccination Against Postoperative Pneumonia and Mortality for Geriatric Patients Receiving Major Surgery: A Nationwide Matched Study.

Limited information is available on the association between influenza vaccination and postoperative outcomes. Using Taiwan's National Health Insurance Research Database reimbursement claims data from 2008-2013, we conducted a matched cohort study of 16903 patients aged >66 years who received influenza vaccinations and later underwent major surgery. Using a propensity score matching procedure adjusted for sociodemographic characteristics, medical condition, surgery type, and anesthesia type, 16903 controls who underwent surgery but were not vaccinated were selected. Logistic regressions were used to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for postoperative pneumonia and in-hospital mortality associated with influenza vaccination. Patients who received preoperative influenza vaccination had a lower risk of postoperative pneumonia (OR, 0.60; 95% CI, .56-.64) and in-hospital mortality (OR, 0.46; 95% CI, .39-.56), compared with unvaccinated patients, in both sexes and every age group. Vaccinated patients who underwent surgery also had a decreased risk of postoperative intensive care unit admission (OR, 0.56; 95% CI, .53-.60), shorter hospital stays (P < .0001), and lower medical expenditures (P < .0001) than nonvaccinated controls. Vaccinated geriatric patients who underwent surgery had lower risks of pneumonia and in-hospital mortality, compared with unvaccinated patients who underwent similar major surgeries. Further studies are needed to explain how preoperative influenza vaccination improves perioperative outcomes.

Does anatomic resection improve the postoperative outcomes of solitary hepatocellular carcinomas located on the liver surface?

BackgroundIt is unclear whether anatomic resection achieves better outcomes than nonanatomic resection in patients with hepatocellular carcinoma. This study aimed to compare the outcomes of anatomic resection and nonanatomic resection for hepatocellular carcinoma located on the liver surface via one-to-one propensity score-matching analysis. MethodsData from all consecutive patients who underwent liver resection for primary solitary hepatocellular carcinoma at Nara Medical University Hospital, Japan, January 2007– December 2015 were retrieved. Superficial hepatocellular carcinomas were defined as hepatocellular carcinoma that extended to a depth of < 3 cm from the liver surface and measured < 5 cm in diameter. The prognoses of the patients with superficial hepatocellular carcinoma who underwent anatomic resection and nonanatomic resection were compared. ResultsIn this study 23 patients with superficial hepatocellular carcinoma underwent anatomic resection and 70 patients who underwent nonanatomic resection. The recurrence-free survival rate of the patients who underwent anatomic resection was better than that of the patients who underwent nonanatomic resection (P = .006), while no such difference was observed for nonsuperficial hepatocellular carcinoma. After the propensity score-matching procedure, the resected liver volume and operation time were the only background or clinical characteristics to exhibit significant differences between the anatomic resection (n = 20) and nonanatomic resection groups (n = 20). The recurrence-free survivial rate of the patients who underwent anatomic resection was significantly than that of the patients that underwent nonanatomic resections (P = .030), but overall survival did not differ significantly between the groups (P = .182). ConclusionAnatomic resection decreases the risk of tumor recurrence and improves recurrence-free survival compared with nonanatomic resection in patients with superficial hepatocellular carcinoma.

P.1.a.040 - Genetic analysis of the endocannabinoid signalling in association with anxious and depressive phenotype

Although routine aspiration thrombectomy (AT) is not recommended by the current American College of Cardiology/American Heart Association/Society for Cardiovascular Angiography and Interventions guideline, for selected cases, a class IIb indication is given because of lack of data. We studied the impact of selective AT on mortality in patients with ST-segment elevation myocardial infarction using a prospective registry. We analyzed data of 1,255 patients, of whom 535 underwent AT based on operator's decision. Separate propensity score matching procedures were performed including all patients and only those with initial TIMI (Thrombolysis In Myocardial Infarction) 0 to 1 flow, indicating the highest thrombus burden. Primary outcome measure was time to all-cause death at 1 year. Both studies were sufficiently powered to detect the hazard ratio (HR) of 0.52 seen in the TAPAS (Thrombus Aspiration during Percutaneous coronary intervention in Acute myocardial infarction Study) trial. In the study with open inclusion criteria, 1-year mortality rates were 15.5% and 14.5% in the AT and conventional percutaneous coronary intervention arm, respectively (p = 0.77). The unadjusted HR was 1.05 (95% CI 0.73 to 1.51), p = 0.80, whereas the adjusted HR was 0.97 (95% CI 0.66 to 1.41), p = 0.87. In patients with initial TIMI 0 to 1 flow, mortality rate at 1 year was 15.6% in the AT and 16.7% in the standard percutaneous coronary intervention group (p = 0.76). The unadjusted and adjusted HRs were similar: 0.91 (95% CI 0.62 to 1.34), p = 0.65 and 0.93 (95% CI 0.62 to 1.37), p = 0.70, respectively. In conclusion, selective AT based on operator's discretion offers no mortality benefit of the magnitude detected in the TAPAS trial, even for patients with initial TIMI 0 to 1 flow grade.

Seeing is not necessarily the truth: Do institutional investors' corporate site visits reduce hosting firms' stock price crash risk?

This study examines the impact of institutional investors' corporate site visits (CSVs) on stock price crash risk. We find that the frequency of institutional investors' CSVs is positively associated with hosting firms' future stock price crash risk. This association is robust to an array of sensitivity checks, including alternative measures of interaction intensity, alternative samples, additional control variables, firm fixed effects model, two-stage instrumental approach, Heckman two-stage sample selection procedure and propensity score matching (PSM) procedure. Further analysis shows that the impact of institutional investors' CSVs on future crash risk is more pronounced when firm managers have higher bad-news hoarding incentives and less information disclosure monitoring, and when firms are plagued more by information asymmetry. Moreover, the economic mechanism analysis shows that the average cumulative abnormal return (CAR) around the announcement day of institutional investors' CSVs is significantly positive, that CSVs have larger effect for firms with higher CARs and that firms visited more by institutional investors are more likely to make financial restatement in future. Overall, our findings are consistent with the notion that institutional investors' CSVs exacerbate managers' incentives to withhold bad news, which leads to bad news accumulation and future stock price crash risk.

Can returnee managers promote CSR performance? Evidence from China

With growing economic globalization, returnee managers who have obtained education or work experience overseas play a much more crucial role in corporations, especially in emerging economies. Using hand-collected managerial background data from a sample of firms listed on the Shanghai and Shenzhen Stock Exchanges from 2010 to 2014, this paper investigates the impact of returnee managers on corporate social responsibility (CSR) performance. We find that returnee managers can promote CSR performance. Further analyses show that the impact of returnee managers on CSR is more pronounced when managers have a foreign study background compared to managers with foreign work experience. The impact only holds when managers obtained their experience in developed economies. When enterprises face greater information asymmetry, returnee managers are more willing to use CSR as a tool to convey a positive image to stakeholders. CSR can help managers reduce information asymmetry and improve firm value. The results are robust through a series of robustness checks including a propensity score matching (PSM) procedure and a Heckman two-state sample selection model. This paper contributes to growing studies on the economic consequences of returnee managers and advances our understanding of the determinants of CSR at the individual level. The results also have implications for government and enterprises attracting talents with overseas experience.

The role of taxes and the interdependence among corporate financial policies: Evidence from a natural experiment

In this paper, we investigate whether and how firms respond to an exogenous tax variation at the investor level by examining their financial decisions following a tax reform for pension funds in Brazil. Consistent with the tax-preference theory of dividends, we find that after implementation of the new law, firms tend to distribute more tax-deductible dividends — called Interest on Equity (IOE) — when the largest or second largest shareholder is a pension fund rather than other types of agents. Surprisingly, control firms also increased (but less than treated firms) their tax-deductible dividend payments, probably to attract more institutional investors and to reduce their cost of capital. We also find that treated firms reduced their leverage relative to control firms after the new law, suggesting that equity tax shields and debt tax shields act as substitute financial instruments. These results are robust to falsification tests and an alternative control group of firms based on a Propensity Score Matching procedure. Overall, our evidence suggests that tax is a first-order determinant of corporate financial decisions and firms adjust their policies in consideration of the interdependence among alternative financial instruments.