The future is yesterday: Use of AI-driven facial recognition to enhance value in the travel and tourism industry.

This study aims to investigate the role of artificial intelligence (AI) driven facial recognition to enhance a value proposition by influencing different areas of services in the travel and tourism industry. We adopted semi-structured interviews to derive insights from 26 respondents. Thematic analysis reveals the development of four main themes (personalization, data-driven service offering, security and safety, and seamless payments). Further, we mapped the impact of AI- driven facial recognition to enhance value and experience for corporate guests. Findings indicate that AI-based facial recognition can facilitate the travel and tourism industry in understanding travelers' needs, optimization of service offers, and value-based services, whereas data-driven services can be realized in the form of customized trip planning, email, and calendar integration, and quick bill summarization. This contributes to strengthening the tourism literature through the lens of organizational information processing theory.

Predicting preventive travel behaviors under the COVID-19 pandemic through an integration of Health Belief Model and Value-Belief-Norm.

This study developed a conceptual framework for a preventive travel decision-making process amidst the COVID-19 pandemic, combining the Health Belief Model (HBM) and Value-Belief-Norm (VBN). Analyzing 409 responses collected from an online survey, this study verified the integrated model as a salient theory addressing the importance of social components and health belief factors in affecting behavior. The model revealed that altruistic value influences the HBM variables, whereas personal norms mediate preventive behaviors and beliefs in both VBN and HBM. These findings offer new theoretical insights into decision-making process and provide practitioners with effective crisis management strategies concerning pro-social and health beliefs.

Impact of perception of COVID-19 on NPI, job satisfaction, and customer orientation: Highlighting three types of NPIs for the airline industry.

Without vaccines or pharmaceutical treatments for a viral pandemic, non-pharmaceutical interventions (NPIs) such as washing hands and wearing masks are likely the most effective ways to control infections at airports and on airplanes. Although the aviation market is a major entry point for viruses, little is known about how flight attendants view the risk of COVID-19 and whether they follow individual-organizational-governmental NPI protocols. Guided by protection motivation theory (Rogers, 1975), this study proposed an NPI model tailored specifically to the airline industry and examined how an extended NPI would affect job satisfaction and customer orientation of Korean flight attendants (n = 371). Results revealed that perceptions of COVID-19 are positively related to three types of NPIs, which in turn positively influenced job satisfaction and customer orientation. Given that the examined three types of NPIs had not been paid attention in previous research, the study's proposed conceptual model should better guide the airline industry in protecting its flight attendants with NPI strategies inside and outside aircraft.

Two-year clinical outcomes after discontinuation of long-term golimumab therapy in Korean patients with rheumatoid arthritis.

BACKGROUND/AIMS: The aim of this study was to investigate long-term post-discontinuation outcomes in patients with rheumatoid arthritis (RA) who had been treated with tumor necrosis factor-α inhibitors (TNF-αi) which was then discontinued. METHODS: Sixty Korean patients with RA who participated in a 5-year GO-BEFORE and GO-FORWARD extension trials were included in this retrospective study. Golimumab was deliberately discontinued after the extension study (baseline). Patients were then followed by their rheumatologists. We reviewed their medical records for 2 years (max 28 months) following golimumab discontinuation. Patients were divided into a maintained benefit (MB) group and a loss-of-benefit (LB) group based on treatment pattern after golimumab discontinuation. The LB group included patients whose conventional disease-modifying antirheumatic drug(s) were stepped-up or added/switched (SC) and those who restarted biologic therapy (RB). RESULTS: The mean age of patients at baseline was 56.5 years and 55 (91.7%) were females. At the end of follow-up, 23 (38.3%) patients remained in the MB group. In the LB group, 75.7% and 24.3% were assigned into SC and RB subgroups, respectively. Fifty percent of patients lost MB after 23.3 months. Demographics and clinical variables at baseline were comparable between MB and LB groups except for age, C-reactive protein level, and corticosteroid use. Restarting biologic therapy was associated with swollen joint count (adjusted hazard ratio [HR], 1.90; 95% confidence interval [CI], 1.01 to 3.55) and disease duration (adjusted HR, 1.12; 95% CI, 1.02 to 1.23) at baseline. CONCLUSION: Treatment strategies after discontinuing TNF-αi are needed to better maintain disease control and quality of life of patients with RA.

Clinical impact of blood pressure variability in patients with COVID-19 and hypertension.

OBJECTIVE: This study aimed to investigate the relationship between blood pressure variability (BPV) and clinical outcomes in patients with coronavirus disease 2019 (COVID-19) and hypertension. METHODS: A total of 136 patients hospitalized with COVID-19 were enrolled in this study. Patients were grouped according to the presence of hypertension and BPV. Mean arterial pressure (MAP) measured at 8 a.m. and 8 p.m. was analyzed, and BPV was calculated as the coefficient of variation of MAP (MAPCV). High BPV was defined as MAPCV values above the median. We compared the age, level of C-reactive protein (CRP), creatine kinase-MB (CK-MB), N-terminal pro-B type natriuretic peptide (NT-proBNP), creatinine and in-hospital mortality and investigated the relationship among the groups. RESULTS: COVID-19 patients with hypertension were older (70 ± 12 vs. 53 ± 17 years; P < 0.001), had higher levels of CRP (9.4 ± 9.2 vs. 5.3 ± 8.2 mg/dL; P = 0.009), MAPCV (11.4 ± 4.8 vs. 8.9 ± 3.2; P = 0.002), and higher in-hospital mortality (19.6% vs. 5.9%; P = 0.013) than those without hypertension. There was a proportional relationship between BPV and age, levels of CRP, CK-MB, NT-proBNP, creatinine and in-hospital mortality (all, P < 0.05). In Cox regression analysis, advanced age [≥80 years, hazard ratio (HR) 10.4, 95% confidence interval (CI) 2.264-47.772, P = 0.003] and higher MAPCV (HR 1.617, 95% CI, 1.281-2.040, P < 0.001) were significantly associated with in-hospital mortality. CONCLUSION: High BPV in COVID-19 patients with hypertension is significantly associated with in-hospital mortality. Advanced age and systemic inflammation are proportional to high BPV. Additional attention is needed for COVID-19 patients with hypertension and high BPV.

Treat-to-Target Strategy for Asian Patients with Early Rheumatoid Arthritis: Result of a Multicenter Trial in Korea.

BACKGROUND: To evaluate the therapeutic benefits of the treat-to-target (T2T) strategy for Asian patients with early rheumatoid arthritis (RA) in Korea. METHODS: In a 1-year, multicenter, open-label strategy trial, 346 patients with early RA were recruited from 20 institutions across Korea and stratified into 2 groups, depending on whether they were recruited by rheumatologists who have adopted the T2T strategy (T2T group) or by rheumatologists who provided usual care (non-T2T group). Data regarding demographics, rheumatoid factor titer, anti-cyclic citrullinated peptide antibody titer, disease activity score of 28 joints (DAS28), and Korean Health Assessment Questionnaire (KHAQ) score were obtained at baseline and after 1 year of treatment. In the T2T group, the prescription for disease-modifying antirheumatic drugs was tailored to the predefined treatment target in each patient, namely remission (DAS28 < 2.6) or low disease activity (LDA) (2.6 ≤ DAS28 < 3.2). RESULTS: Data were available for 163 T2T patients and 162 non-T2T patients. At the end of the study period, clinical outcomes were better in the T2T group than in the non-T2T group (LDA or remission, 59.5% vs. 35.8%; P < 0.001; remission, 43.6% vs. 19.8%; P < 0.001). Compared with non-T2T, T2T was also associated with higher rate of good European League Against Rheumatism response (63.0% vs. 39.8%; P < 0.001), improved KHAQ scores (-0.38 vs. -0.13; P = 0.008), and higher frequency of follow-up visits (5.0 vs. 2.0 visits/year; P < 0.001). CONCLUSION: In Asian patients with early RA, T2T improves disease activity and physical function. Setting a pre-defined treatment target in terms of DAS28 is recommended.

Factors associated with quality of life and functional disability among rheumatoid arthritis patients treated with disease-modifying anti-rheumatic drugs for at least 6 months.

AIM: To determine characteristics of rheumatoid arthritis (RA) patients in Korea using disease-modifying anti-rheumatic drugs (DMARDs) for at least 6 months, and to identify factors associated with poor health-related outcomes. METHOD: A total of 2000 RA patients aged > 20 years, treated with DMARDs for at least 6 months, and signed informed consent, were enrolled in this non-interventional, multicenter, cross-sectional observational study from December 2012 to June 2013. Health-related quality of life (HRQoL) was measured using EuroQuol 5D (EQ-5D) and functional disability was measured using the Korean Health Assessment Questionnaire (KHAQ). Univariate and multivariate linear regression analyses were used to determine the association between patient characteristics and patient-reported outcomes (PROs). RESULTS: Of all RA patients, 84% were female, patients with low Disease Activity Score of 28 joints erythrocyte sedimentation rate (DAS-28-ESR < 3.2) was 54%, while moderate (DAS-28-ESR 3.2-5.1) and high disease activity score (DAS-28-ESR > 5.1) were 38% and 7.6%, respectively. Mean EQ-5D index score and KHAQ score were 0.6 ± 0.28 and 0.7 ± 0.67, respectively. In multivariate analysis with both PROs, average HRQoL and functional disability score appeared to be worse in persons with older age compared to younger age (P < 0.001), and worse in females compared to males (P < 0.001). Compared to patients having lower DAS (< 3.2), those with moderate and highest DAS (3.2-5.1 and > 5.1) had worse outcome measures (P < 0.001). CONCLUSION: In this study, higher DAS was one of the most influential factors for poor PROs among all other factors. Therefore, we could suggest appropriate treatment approaches according to DAS along with other significantly associated factors with PROs in the early stage of RA.

Factors Contributing to Discordance between the 2011 ACR/EULAR Criteria and Physician Clinical Judgment for the Identification of Remission in Patients with Rheumatoid Arthritis.

Remission is a primary end point of in clinical practice and trials of treatments for rheumatoid arthritis (RA). The 2011 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) remission criteria were developed to provide a consensus definition of remission. This study aimed to assess the concordance between the new remission criteria and the physician's clinical judgment of remission and also to identify factors that affect the discordance between these two approaches. A total of 3,209 patients with RA were included from the KORean Observational Study Network for Arthritis (KORONA) database. The frequency of remission was evaluated based on each approach. The agreement between the results was estimated by Cohen's kappa (κ). Patients with remission according to the 2011 ACR/EULAR criteria (i.e. the Boolean criteria) and/or physician judgment (n = 855) were divided into three groups: concordant remission, the Boolean criteria only, and physician judgment only. Multinomial logistic regression analysis was used to identify factors responsible for the assignment of patients with remission to one of the discordant groups rather than the concordant group. The remission rates using the Boolean criteria and physician judgment were 10.5% and 19.9%, respectively. The agreement between two approaches for remission was low (κ = 0.226) and the concordant remission rate was only 5.5% (n = 177). Pain affected classification in both discordant groups, whereas fatigue was associated with remission only by physician clinical judgment. The Boolean criteria were more stringent than clinical judgment. Patient subjective symptoms such as pain and fatigue were associated with discordance between the two approaches.

Effects of Methotrexate on Carotid Intima-media Thickness in Patients with Rheumatoid Arthritis.

The purpose of this study was to evaluate the effects of rheumatoid arthritis (RA) and antirheumatic drugs on atherosclerosis by comparing carotid intima-media thickness (CIMT) as an indicator for cardiovascular diseases (CVD). This study included 44 female RA patients who met the 2010 ACR/EULAR criteria and age-matched 22 healthy females. CIMT was measured on both carotid arteries using a B-mode ultrasound scan. The mean value of both sides was taken as the CIMT of the subject. The CIMT was evaluated according to the use of drugs, disease activity and CVD risk factors in RA patients as a case-control study. Higher CIMT was observed in RA patients as compared with healthy subjects (0.705 ± 0.198 mm, 0.611 ± 0.093 mm, respectively, P < 0.05). With adjustment for the CVD risk factors, disease activity and the use of anti-rheumatic drugs, methotrexate (MTX) only showed a favorable effect on CIMT in RA. A significantly lower CIMT was observed in RA with MTX as compared with RA without MTX (0.644 ± 0.136 mm, 0.767 ± 0.233 mm, respectively, P < 0.05). The effects were correlated with MTX dosage (ß = -0.029, P < 0.01). The use of MTX should be considered in high priority not only to control arthritis but also to reduce the RA-related CVD risk to mortality.

Age-related NADPH Oxidase (arNOX) Activity Correlated with Cartilage Degradation and Bony Changes in Age-related Osteoarthritis.

The purpose of this study was to investigate the age-related NADPH oxidase (arNOX) activity in patients with age-related knee osteoarthritis (OA). Serum and cartilage arNOX activities were determined using an oxidized ferricytochrome C reduction assay. Full-thickness knee joint cartilages obtained through total knee replacement surgery were graded according to the Outerbridge (OB) classification. Radiographic severity of OA was determined on Knee X-rays according to the Kellgren-Lawrence (K/L) grading system. Cartilage ß-galactosidase, HIF-1α, and GLUT-1 expression levels were evaluated as markers for tissue senescence, hypoxia, and glycolysis. Higher arNOX activities occurred with higher levels of cartilage ß-galactosidase, HIF-1α, and GLUT-1 (P = 0.002). arNOX activity in cartilages with surface defects (OB grade II, III) was higher than in those without the defects (OB grade 0, I) (P = 0.012). Cartilage arNOX activity showed a positive correlation with serum arNOX activity (r = -0.577, P = 0.023). Serum arNOX activity was significantly higher in the OA subgroup with bilateral ROA than in the OA with no or unilateral ROA (2.449 ± 0.81, 2.022 ± 0.251 nM/mL, respectively, P = 0.019). The results of this study demonstrate that OA itself is not a cause to increase arNOX activities, however, arNOX hyperactivity is related to a high degree of cartilage degradation, and a high grade and extent of ROA in age-related OA.

Differential Gambling Motivations and Recreational Activity Preferences Among Casino Gamblers.

This study investigated three different types of gamblers (recreational, problem, and pathological gamblers) to determine differences in gambling motivations and recreational activity preferences among casino gamblers. We collected data from 600 gamblers recruited in an actual gambling environment inside a major casino in South Korea. Findings indicate that motivational factors of escape, sightseeing, and winning were significantly different among these three types of gamblers. When looking at motivations to visit the casino, pathological gamblers were more likely to be motivated by winning, whereas recreational gamblers were more likely to be motivated by scenery and culture in the surrounding casino area. Meanwhile, the problem gamblers fell between these two groups, indicating higher preferences for non-gambling activities than the pathological gamblers. As this study builds upon a foundational previous study by Lee et al. (Psychiatry Investig 6(3):141-149, 2009), the results of this new study were compared with those of the previous study to see if new developments within a resort-style casino contribute to changes in motivations and recreational activity preferences.

Reliability and Validity of Three Instruments (DSM-IV, CPGI, and PPGM) in the Assessment of Problem Gambling in South Korea.

Most research on the assessment, epidemiology, and treatment of problem gambling has occurred in Western jurisdictions. This potentially limits the cross-cultural validity of problem gambling assessment instruments as well as etiological models of problem gambling. The primary objective of the present research was to investigate the reliability and validity of three problem gambling assessment instruments within a South Korean context. A total of 4,330 South Korean adults participated in a comprehensive assessment of their gambling behavior that included the administration of the DSM-IV criteria for pathological gambling (NODS), the Canadian Problem Gambling Index (CPGI), and the Problem and Pathological Gambling Measure (PPGM). Cronbach alpha showed that all three instruments had good internal consistency. Concurrent validity was established by the significant associations observed between scores on the instruments and measures of gambling involvement (number of gambling formats engaged in; frequency of gambling; and gambling expenditure). Most importantly, kappa statistics showed that all instruments have satisfactory classification accuracy against clinical assessment of problem gambling conducted by South Korean clinicians (NODS κ = .66; PPGM κ = .62; CPGI κ = .51). These results confirm that Western-derived operationalizations of problem gambling have applicability in a South Korean setting.

Examining the structural relationships among gambling motivation, passion, and consequences of internet sports betting.

The rise in popularity of Internet gambling has led to new gambling controversies among researchers and policymakers alike. Opponents frequently point to the negative impacts of problem gambling, while advocates tend to view this form of gambling as relatively harmless and convenient entertainment for the vast majority of participants. Interestingly, in making their points, both sides cite empirical arguments about passion for the gambling act-with opponents arguing that Internet gambling enables unhealthy obsessions, and advocates pointing to the apparent intensive interest of large numbers of Internet players. As it turns out, both sides may have a point. In this paper, we examine whether types of passion were related to types of motivation and consequences. The data were collected through a sample from an online gambling website in South Korea. We rely upon Rousseau et al.'s (J Gambl Stud 18(1):45-66, 2002) seminal work on positive and negative aspects of passion, and in the process we develop a framework for understanding positive and negative consequences of this form of gambling. The results reveal that intrinsic gambling motivations (e.g., gambling for excitement) is related to harmonious passion, which in turn results in positive consequences. Meanwhile, extrinsic gambling motivations (e.g., money) is related to obsessive passion, which in turn results in negative consequences.

The role of responsible gambling strategy and gambling passion in the online gamblers' decision-making process: revising the theory of planned behavior.

This study revised the theory of planned behavior (TPB) by incorporating the new concepts of gambling passion and responsible gambling strategy (RGS) to predict gamblers' intention to gamble in online sports betting. The data were collected at the end of March in 2012 through an online gambling website. The findings indicated that the inclusion of two types of gambling passion and two types of RGS explains online gambling intention well. Specifically, out of the original antecedent predictors of TPB, attitude toward online gambling was positively related to harmonious passion. Subjective norm had a positive relationship with both harmonious and obsessive passion. The results also showed that perceived behavioral control does not have a significant effect on the two gambling passions but has a direct and significant influence on behavioral intention. Additionally, the compulsory RGS had a negative effect on obsessive passion, whereas supplementary RGS had concurrent positive impacts on harmonious and obsessive passion. Lastly, the two gambling passions were notable predictors of behavioral intention toward online sports betting.

Effects of hypoxia/ischemia on catabolic mediators of cartilage in a human chondrocyte, SW1353.

Cells from a human chondrocyte cell line were studied in 1% oxygen and/or a lower glucose concentration (5.5 mM), compared to the routine culture conditions of normoxia and high glucose. HIF-1α, IL-1ß, IL-6, IL-8, COX-2, TNFα, LIF, MMP-3, MMP-13, and reactive oxygen species (ROS) were evaluated, respectively. Effects of hypoxia inducing expression of HIF-1α were statistically significant at 72 h (p<0.05). Increased production of ROS by hypoxia was also observed with passage of time (p<0.05). The effects of hypoxia on HIF-1α and IL-1ß were potentiated by 5.5 mM glucose, especially after 48 h (p<0.05). IL-8 production was significantly induced in 1% O(2), with 5.5 mM glucose (p<0.01). IL-8 mRNA expression and production in response to IL-1ß were potentiated by hypoxia/ischemia (p<0.05, p<0.01, respectively). Up-regulation of IL-1ß, ROS, and IL-8 by hypoxia/ischemia in human chondrocytes may occur in correlation with HIF-1α. IL-8 response to IL-1ß may be potentiated synergically by hypoxia/ischemia, as an effector of hypoxia/ischemia. The results may suggest aggressive biology of the ordinary cartilage hypoxia/ischemia in the context of arthro-degeneration.

The prevalence and nature of gambling and problem gambling in South Korea.

PURPOSE: To establish the current prevalence of gambling and problem gambling in South Korea and to determine the associated demographic and game play patterns. METHODS: Administration of a gambling survey over the phone to 4,000 randomly selected South Korean adults (19+), supplemented by an online survey of 4,330 members of a South Korean online panel. RESULTS: The past year prevalence of gambling among South Korean adults was 41.8 %. The past year engagement in individual forms of gambling was 36.2 % for lotteries and instant lotteries; 12.0 % for social gambling; 2.3 % for sports betting; 1.5 % for casino gambling; 1.5 % for internet gambling; and 1.1 % for horse, bicycle, or motor boat betting. The past year prevalence of problem gambling was 0.5 %. Logistic regression identified the best predictors of problem gambling to be: having a greater number of gambling fallacies; gambling on the internet; betting on horses, bicycling, or motor boat racing; social gambling; male gender; mental health problems; sports betting; motivation for gambling (gambling to escape); casino gambling; and lower income. CONCLUSIONS: The past year prevalence of gambling (41.8 %) and problem gambling (0.5 %) in South Korea is low compared to other countries, especially relative to other Asian jurisdictions. This relatively low prevalence of gambling is likely related to the very strong negative attitudes toward it, the low participation by females, and restricted access. The low prevalence of problem gambling is likely related to the relatively low prevalence of gambling and restricted access to continuous forms of gambling. The variables that are predictive of problem gambling in South Korea are quite similar to those found in other countries with a couple of important differences.

Examining antecedents and consequences of gambling passion: the case of gambling on horse races.

OBJECTIVE: This study investigated the antecedents and consequences of gambling passion using structural equation modeling to examine relationships among gambling motivation, passion, emotion, and behavioral intentions in the horse racing industry. METHODS: An onsite survey was conducted with 447 patrons at a horseracing park in South Korea. A confirmatory factor analysis showed that the Gambling Passion Scale was valid and reliable, resulting in two sub-scales: obsessive passion (OP) and harmonious passion (HP). RESULTS: Study results indicated that extrinsic motivation influenced OP whereas intrinsic motivation significantly affected HP. Furthermore, OP was correlated with negative emotion, whereas HP was related to positive emotion. Gamblers' satisfaction was found to be influenced positively by positive emotion and negatively by negative emotion. Finally, satisfaction appeared to affect gamblers' behavioral intentions. CONCLUSION: Study results echoed the notion of distinct and separate gambling motivations and passions among horse racing gamblers. Furthermore, results identified specific areas to which horse racing operators or policy makers should pay special attention in developing effective marketing strategies to promote responsible gambling.

The impact of non-pharmaceutical interventions for 2009 H1N1 influenza on travel intentions: A model of goal-directed behavior.

Theoretically, in the tourism context this study introduced a new concept of non-pharmaceutical intervention (NPI) for influenza, and tested the impact of NPI on the behavioral intention of potential international tourists. This study also extended the model of goal-directed behavior (MGB) by incorporating the new concepts of NPI, and the perception of 2009 H1N1. The model found that desire, perceived behavioral control, frequency of past behavior, and non-pharmaceutical interventions predicted tourists' intention but perceptions of 2009 H1N1 had nil effect on desire and intention. Personal non-pharmaceutical interventions were theorized as adaptive behavior of tourists intending to travel during a pandemic which should be supported by tourism operators on a system-wide basis. Practically, this study dealt with the issue of influenza 2009 H1N1 with the study findings and implications providing government agencies, tourism marketers, policy-makers, transport systems, and hospitality services with important suggestions for NPI and international tourism during pandemics.

Korean Observational Study Network for Arthritis (KORONA): establishment of a prospective multicenter cohort for rheumatoid arthritis in South Korea.

OBJECTIVES: The object of this study was to introduce the KORean Observational study Network for Arthritis (KORONA) registry with an emphasis on the design of the Korean rheumatoid arthritis (RA) national database, as well as to provide an overview of the RA patients who are currently registered in KORONA. METHODS: The KORONA was established in July 2009 by the Clinical Research Center for Rheumatoid Arthritis (CRCRA) in South Korea. KORONA is based on a prospective protocol and standard, defined data collection instruments. Demographic and clinical features, laboratory and radiologic data, health-related outcomes, treatment side effects, resource utilization, and health behaviors of the RA cohort patients are recorded in a database. RESULTS: A total of 23 institutions, which are about 38% of the rheumatologic departments at tertiary academic hospitals across South Korea, are part of KORONA. The quality control of data collection and management has been performed through annual monitoring and auditing, staff training, and providing standard operation protocol by the executive committee of CRCRA. As of 31 December 2010, 4721 patients with established RA were included in KORONA, because an annual survey had started to be performed in July 2010. CONCLUSIONS: KORONA is the first nationwide Korean RA-specific cohort and it will provide valuable "real-world" information for Korean RA patients.

Development of a bias ratio to examine factors influencing hypothetical bias.

Using data from three contingent valuation studies, this study investigates if socio-economic factors and the type of good being valued can help explain changes in respondents' answers. A bias ratio, defined as the ratio of respondents who change their choice under hypothetical and "real" settings, is developed to help explain changes in respondents' answers. Marginal changes in the bias ratio resulting from a change in a particular independent variable consist of changes in responses in both the hypothetical and real situation. Results provide limited evidence that socio-economic variables and type of good being study can help in explaining bias. Respondents who are older, have a higher level of education, and are environmentally conscious tend to show less bias. Familiarity with the good also tend to decrease bias. A large amount of the variation in bias, however, remains unexplained.