• Journal of Chest Surgery
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• v.51 no.6
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• pp.367-375
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• 2018

Background: It is unclear whether mitral valve (MV) repair for degenerative mitral regurgitation (MR) provides the same advantages in the elderly that it does in the general population. Methods: From 1994 to 2016, 188 elderly patients (mean age, $68.3{\pm}5.50years$) underwent MV repair (n=153) or MV replacement (n=35) for primary degenerative MR. Early and long-term outcomes were compared before and after propensity score matching (PSM). Results: Before PSM, there was a significant difference in operative mortality (p=0.011). Overall survival and freedom from cardiac-related death (CRD) at 5, 10, and 15 years were significantly higher in patients who underwent MV repair (p=0.039 and p=0.007, respectively). In the multivariable analysis, MV replacement was an independent risk factor of CRD. After PSM, operative mortality was not significantly lower in patients who underwent MV repair (p=0.125). Overall survival and freedom from CRD at 5, 10, and 15 years showed no significant difference between the 2 groups in the PSM cohort (p=0.207, p=0.47, respectively). There was no significant difference in freedom from reoperation before or after PSM (p=0.963 and p=0.575, respectively). Conclusion: MV repair for primary degenerative MR might be a valid option in the elderly population if successful repair is possible.

• Journal of Labour Economics
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• v.43 no.3
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• pp.33-61
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• 2020

The purpose of this study is to analyze the disparity in on-the-job training between regular and non-regular workers and to compare the wage effects of on-the-job training. Using the Korean micro data from the Programme for the International Assessment of Adult Competencies(PIAAC) published by OECD, Propensity Score Method(PSM) is applied to overcome the endogeneity problem. The average treatment effect(ATT) on the training participation is analyzed, using non-regular workers as treatment group and regular workers as comparison group. Odds ratios of non-regular employees' training participation compared to regular employees shows 0.67 times after constructing matching sample and this means that non-regular workers are facing a disadvantageous training opportunity compared to regular workers. In order to estimate the wage effect of on-the-job training, the average treatment effect(ATT) of on-the-job training on average wages for regular workers and non-regular workers is estimated respectively. I find insignificant wage effect from on-the-job training among regular workers and significant positive effect on non-regular worker's wage from on-the-job training.

• The Journal of Korean Society for School & Community Health Education
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• v.22 no.2
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• pp.1-14
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• 2021

Objectives: The study aimed to analyze the effects of household financial difficulties caused by COVID-19 (2019 coronavirus disease) on suicidal tendencies of adolescents. Methods: We selected 54,948 middle and high school students who were surveyed based on the Korean Youth Risk Behavior Web-based Survey 2020. To analyze the data, we used the STATA 16.0 program to conduct propensity score matching (PSM). Results: After controlling for selection effects by using PSM, the household financial difficulties caused by COVID-19 maintained a significant predictive effect on increasing suicidal ideation, suicide attempts, and decreasing tendency in hospital-treated after suicide attempts. However, depressive symptoms and suicide plan did not show a significant correlation with household financial difficulties associated with COVID-19. Conclusions: It was found that the rate of suicidal ideation and suicide attempts among adolescents who experienced a household financial difficulties due to COVID-19. Therefore, It can provide empirical evidence for estimating the impact of COVID-19 on adolescent suicide rates.

• Journal of Korea Technology Innovation Society
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• v.14 no.3
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• pp.689-710
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• 2011

The purpose of this paper is to positively analyze firms' innovative performance enhanced by cooperation, such as industry-university or industry-government, in service industry. We use PSM method (Propensity Score Matching) based on Korea Innovation Survey data in service industry to investigate it. This empirical study finds that cooperation with university or government partially has positive effects on firm's patent applications and innovation. So, we suggest we need various policies for research institute linkage in service industry.

• KDI Journal of Economic Policy
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• v.32 no.2
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• pp.27-53
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• 2010

This paper examines whether and how much vocational training raises an individual's earnings in Korea, using the Economically Active Population Survey. To overcome endogeneity of training, we apply fixed-effects and propensity-score matching (PSM) methods. Fixed-effects (PSM) results suggest that work-related training received in the previous one year increases a worker's monthly earnings by 2.6 to 4.7 (7.5 to 9.8) percent. Taken altogether, work-related training enhances a worker's earnings by a minimum of 2.6 and a maximum of 9.8 percent in Korea.

• Journal of Technology Innovation
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• v.31 no.3
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• pp.201-230
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• 2023

The Innovation Procurement Policy was introduced as part of the strategic public procurement policy to improve firms' innovation capabilities and enhance the public sector's ability to solve social problems by designating and purchasing so-called 'innovative products.' The pilot procurement project for innovative products was first introduced in 2019, and the policy system for designating and discovering innovative products by government departments, as well as the priority purchase system, was established in 2020. Hence, this study conducted a quantitative analysis focusing on the effectiveness of the innovation procurement system in supporting firms after it was fully implemented. For this purpose, corporate financial and employment data from 2017 to 2021 were used, and propensity score matching(PSM) and difference-in-difference(DID) methods were utilized as analytical tools. The study found that the innovation procurement system contributed to corporate growth and employment and created additional public and private sales channels. Moreover, it is necessary to enhance the innovation procurement system, such as matching innovative product-producing companies with existing SME support policies, for companies to become self-sustaining after the innovative product designation ends.

• Korea Trade Review
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• v.46 no.2
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• pp.323-335
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• 2021

With the advent of the 4th Industrial Revolution, there is a rising interest in the impact of these changes on Korea's trade. While the previous studies related to the 4th Industrial Revolution are very limited in the field of trade research, this study attempts an empirical analysis regarding the effect of the use of the 4th Industrial Revolution technology on the performance of exporters, based on the data of the Survey of Business Activities during 2017-2019 by the Korean government statistical office. Through the empirical analysis in combination with the propensity score matching (PSM) and the difference-in-difference (DID) analysis, this research confirms that the use of the 4th Industrial Revolution technology has a positive effect on the export performance of Korean exporters.

• Journal of Distribution Science
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• v.16 no.1
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• pp.87-99
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• 2018

Purpose - The Export Infrastructure Strengthening Program(EISP) is a project to expand exports of agri-food products through providing customized export information to food distribution companies and supporting overseas information activities. A total of 39.6 billion won was provided by 2016. So, the purpose of this study is to analyze whether EISP is effective for expanding exports of agri-food products. Research design, data, and methodology - A simple average difference between the export performance of the policy beneficiaries and the non-policy beneficiaries can be biased if the export capacity or inherent characteristics of the enterprise are not taken into consideration. In order to solve the problem of such a bias, the propensity score matching(PSM) method has been employed in this study. PSM is a method of converting the characteristics of an export company into an index through logit analysis and then reducing the matching to one dimension to improve the accuracy of the performance measurement. Results - The balancing test was conducted to determine how the characteristics of the policy beneficiary group and the matched policy non-beneficiary group corresponded to each other. As a result of the test, we could not reject the null hypothesis that there was no difference between the two groups, so that after the matching, the two groups were similar and the explanatory variables were well controlled. Using the nearest neighbor matching with propensity score estimating through logit analysis, we estimated average treatment effect on the treated(ATT). The food companies participating the EISP had the effect of increasing the exports of $ 5.88 million. As a result, the number of export contracts increased by 11.77, the number of exporting countries by 7.52, the number of export items by 47.51, and the number of buyers' consultation by 3.50. And overseas marketing expenses increased by 35.92 million won. Except for the number of export contracts, other export performance results showed statistically significant results. Conclusions - As the EISP has a positive effect on the expansion of agro-food exports, efforts should be made to find out the limitations or problems of the policy in the future and to make a greater contribution to the increase of exports.

• Clinics in Shoulder and Elbow
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• v.26 no.3
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• pp.276-286
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• 2023

Background: The transosseous anchorless repair (ToR) technique was recently introduced to avoid suture anchor-related problems. While favorable outcomes of the ToR technique have been reported, no previous studies on peri-implant cyst formation with the ToR technique exist. Therefore, this study compared the clinical outcomes and prevalence of peri-implant cyst formation between the ToR technique and the conventional transosseous equivalent technique using suture anchors (SA). Methods: Cases with arthroscopic rotator cuff repair (ARCR) between 2016 and 2018 treated with the double-row suture bridge technique were retrospectively reviewed. Patients were divided into ToR and SA groups. To compare clinical outcomes, 19 ToR and 57 SA cases without intraoperative implant failure were selected using propensity score matching (PSM). While intraoperative implant failure rate was analyzed before PSM, retear rate, peri-implant cyst formation rate, and functional outcomes were compared after PSM. Results: The intraoperative implant failure rate (ToR, 8% vs. SA, 15.3%) and retear rate (ToR, 5.3% vs. SA, 19.3%) did not differ between the two groups (all P>0.05). However, peri-implant cysts were not observed in the ToR group, while they were observed in 16.7% of the SA group (P=0.008). Postoperative functional outcomes were not significantly different between the two groups (all P>0.05). Conclusions: The ToR technique produced comparable clinical outcomes to conventional techniques. Considering the prospect of potential additional surgeries, the absence of peri-implant cyst formation might be an advantage of ToR. Furthermore, ToR might reduce the medical costs related to suture anchors and, thereby, could be a useful option for ARCR. Level of evidence: III.

• Korean Journal of Social Welfare
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• v.63 no.4
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• pp.301-326
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• 2011

The major purpose of this study is to evaluate the impact of the long-term care insurance program. In order to estimate the impact of policy accurately, certain bias which might hamper the validity of this study has been removed by Propensity Score Matching(PSM) and Double Difference(DD) method from the semi-experimental design. To study the effects of long-term care insurance on the elderly and their family members as social outcome variable sand the quality of life of their family and satisfaction in family relationships, the third and fourth waves of Korea Welfare Panel are used to match experimental and comparative groups by the propensity score matching. Then, DD method, using the panel fixed effects model, is applied to estimate the differences of those groups'treatment effects before and after the policy implementation. As a result, it was found that the Quality of life on the elderly and their family members is statistically meaningless, while the satisfaction in family relationships has much increased after the policy implementation. The result has a limitation in that this evaluation is performed at the point when the long-term insurance program has not been ripened enough. However, there is an important implication on the significance of realizing the main goal of the long-term care insurance to improve the quality of life of the elderly and their family members and as for the potentiality of further system improvements.