Recently, as the concept of beauty has become more generalized, the desire for physical health and beauty has increased. This can be considered a time when appearance plays a crucial role in social competitiveness, and industries related to appearance are rapidly advancing [1]. Appearance not only acts as a significant factor in determining a person’s impression but is also perceived as a crucial element in social evaluation. Furthermore, expressing likability to others in daily life can be a vital means for successful interpersonal relationships. With the rise of appearance discrimination and aesthetic capitalization in capitalist societies, the focus on appearance among university students has increased, and methods for managing appearance have become diverse. However, with the shift to remote activities and the mandatory use of masks due to coronavirus disease 2019 (COVID-19), the necessity for makeup has decreased, leading to a significant reduction in interest in appearance management and cosmetic purchases.

The social environment created by the COVID-19 pandemic has changed the concept of appearance management. Previous studies on appearance management behavior and self-esteem included those by Ahn [2], who investigated the impact of body image and self-esteem on appearance management behavior in male university students; Park [3], who examined the influence of appearance management behavior on appearance satisfaction and self-esteem in university students in Gwangju; and Han [4], who explored the impact of appearance management attitudes of security majors on self-esteem and career preparation behavior. However, these studies were conducted before the occurrence of COVID-19, and there is a lack of research on beauty majors after the onset of COVID-19. Further research is required in this regard.

This study aimed to clarify the impact of appearance management behavior on self-esteem among university students majoring in beauty in the post-COVID-19 social context. The purpose of this study was to provide foundational data for beauty studies to support healthy and desirable appearance management and foster positive self-esteem.

Appearance management behavior

In interpersonal relationships, appearance plays a crucial role, and a person’s appearance has a significant impact on the formation of the ‘first impression’ in initial encounters. In this context, appearance management behavior refers to actions taken to present oneself in the way one desires others, including hair and skin care, makeup, exercise, or diet for weight control and the purchase and wearing of clothing for body shape correction [5]. Here, appearance encompasses outward features, including facial expressions, clothing, physique, and atmosphere, and plays a central role in the formation and expression of self-concept [6]. Therefore, appearance is an essential element in expressing one’s image to others, and is a crucial factor in representing oneself in interpersonal relationships.

Appearance management is a process in social situations that reveals one’s identity to others. This involves conveying the meaning of visual symbols related to appearance, making sense of oneself through various processes, and internalizing the created visual image [7]. Appearance management behavior can be explained by Maslow’s hierarchy of needs. According to this theory, humans have physiological, safety, social, esteem, and self-actualization needs, forming a hierarchy where the importance of each need increases as one progresses to higher levels, influencing behavior [8]. Appearance management behavior satisfies fundamental aesthetic desires and serves as a means of self-expression to present one’s appearance in a more sophisticated and attractive image. It involves internalizing the meaning of the physical characteristics used as cues when perceiving others and transforming them into one’s own image. Therefore, appearance management behaviors, through various tools for managing appearance, play a significant role in presenting oneself as expected to others, aiming to receive positive perceptions and evaluations in interpersonal relationships.

Research on appearance management has been conducted since the 1990s, and scholars have been studying the relationship between appearance management and psychology since the 2000s. Recently, increased exposure to various media and lifestyle changes have led to a higher quantity and quality of information about appearance, thereby increasing public interest. Additionally, the recognition that appearance influences social activities, relationships, and job opportunities has sparked active research on the utility of appearance management behaviors. Kaiser (1990) defined appearance management as a way of expressing oneself to others in social life, a process through which individuals express their personalities through mutual relationships with others [9,10]. According to Jeong’s study [11] on appearance improvement behaviors among female college students, appearance plays a significant role in interpersonal relationships, especially in influencing first impressions. Thus, appearance is a crucial element in social life as a value and in self-development. Appearance management is a fundamental desire for self-development that increases self-esteem and happiness.

Self-esteem

Self-esteem refers to the degree to which individuals respect themselves. James (1890), who first introduced the concept of the self, defined it as “everything an individual can call their own” and mentioned that it is formed through the interaction between the individual and the social environment in four dimensions: material self, spiritual self, social self, and pure self [12,13]. According to Maslow (1968), self-esteem is one of the five human needs closely related to desires for love and belonging, involving emotions where individuals feel themselves to be beings worthy of interest, recognition, and respect. Most individuals desire stable self-esteem, positive evaluations, and respect for themselves or others [14,15]. If the concept of the self encompasses subjective evaluations of various aspects such as personality, emotions, thoughts, abilities, will, and appearance, self-esteem signifies the positive or negative evaluations an individual holds about themselves [16].

Although scholars may define the concept of self-esteem somewhat differently, there is a consensus that self-esteem plays a crucial role in influencing subjective thoughts and behaviors and impacting individual lives. Self-esteem is defined in various ways and is often used interchangeably with other terms such as self-confidence, self-acceptance, self-concept, self-identity, self-efficacy, self-evaluation, and self-respect. The term self-concept is sometimes used interchangeably with self-esteem, causing confusion among scholars [17]. Self-esteem is considered a vital element in personal adaptation, healthy personality development, self-realization, and influences behavior, emotions, motivations, achievements, and human relationships. Prior research on self-esteem includes studies are as follow. Park’s study [18] of gifted adolescents reported that students with higher self-esteem were more successful in school, had a positive attitude toward school, exhibited positive behaviors in the classroom, and achieved popularity in school. Furthermore, Lee [19] focused on university students and found that many students experiencing maladjustment in university life had low self-esteem, indicating negative perceptions of their current situation and future. Research on the association between self-esteem and school life has been actively conducted, particularly among adolescents and university students. The results indicated that higher self-esteem was associated with positivity, and lower self-esteem was associated with negativity. This demonstrates the crucial role of self-esteem as a significant factor influencing school life and human relationships. Therefore, this study aimed to analyze the impact of appearance management behavior on self-esteem through a survey targeting beauty major university students to assess the enhancement of self-esteem.

Participants and procedures

This study investigated the impact of appearance management behaviors on self-esteem among university students majoring in beauty, specifically focusing on the period after COVID-19. The survey was conducted between April 12 and 26, 2023. Questionnaires were distributed using Naver Form, and 253 responses were collected and processed for final statistical analysis.

Data analysis methods

The data collected for this study were analyzed using SPSS 25.0 (IBM Co.), and the analyses were validated at a significance level of 0.05. First, frequency analysis was conducted to understand the general characteristics of the surveyed participants. Second, to validate the measurement tool, exploratory factor analysis was performed, and reliability verification was conducted using Cronbach’s α coefficient. Third, to examine the appearance management behavior and self-esteem of beauty major university students after COVID-19, and to determine whether there were differences based on the general characteristics of the surveyed subjects, independent sample t-tests and one-way analysis of variance were conducted. Post-hoc tests were performed using Duncan’s test. Fourth, correlation analysis was conducted to explore the correlations between the variables. Multiple regression analysis was then performed to examine the impact of appearance management behavior on self-esteem among university students majoring in beauty after COVID-19.

Study participants

The results of the frequency analysis conducted to understand the general characteristics of the surveyed participants are presented in Table 1. The analysis revealed that out of the participants, 41 were males (16.2%) and 212 were females (83.8%). Regarding academic year, there were 68 first-year students (26.9%), 82 second-year students (32.4%), 26 third-year students (10.3%), and 77 fourth-year students (30.4%). Makeup had 102 participants (40.3%), skincare had 72 participants (28.5%), hair had 57 participants (22.5%) and 22 participants (8.7%) did not specify. In terms of monthly allowance, it was reported that less than 100,000 won by 23 participants (9.1%), 100,000–300,000 won by 51 participants (20.2%), 300,000–500,000 won by 70 participants (27.7%), and more than 500,000 won by 109 participants (43.1%).

Table 1 . Study participants.

Category	Frequency (%)
Sex
Male	41 (16.2)
Female	212 (83.8)
Grade
1st-year	68 (26.9)
2nd-year	82 (32.4)
3rd-year	26 (10.3)
4th-year	77 (30.4)
Major
Hair	57 (22.5)
Skin	72 (28.5)
Makeup	102 (40.3)
Nail	22 (8.7)
Average monthly pocket money
>100,000 won	23 (9.1)
>100,000–300,000 won	51 (20.2)
>300,000–500,000 won	70 (27.7)
<500,000 won	109 (43.1)
Total	253 (100.0)

Validity and reliability verification for appearance management behavior

The validity and reliability of the appearance management behaviors were analyzed, as shown in Table 2. First, the Kaiser-Meyer-Olkin (KMO) value was 0.870, indicating that the sample was suitable for factor analysis. Bartlett’s test result was significant at 4,825.997 (df=300, p=0.000). Five factors with eigenvalues greater than one were extracted, and the overall explanatory power was 73.941%. The subfactors of skin management behavior, makeup management behavior, apparel management behavior, hair management behavior, and body shape management behavior accounted for 17.059%, 15.249%, 14.847%, 13.832%, and 12.953%, respectively. Additionally, the reliability analysis using Cronbach’s α coefficient showed values between 0.855 and 0.938, indicating highly reliable measurement items.

Table 2 . Validity and reliability verification of appearance management behaviors.

Question	Factors (management behavior)
	Skin	Makeup	Apparel	Hair	Body shape
1. When I have skin problems, I go to a specialist.	0.934	0.018	0.009	0.117	0.060
2. I visit a skin care salon to get my skin taken care of.	0.919	0.015	0.073	0.043	0.057
4. I’ve been exposed to information about my skin and put it into practice.	0.893	0.065	0.046	0.080	0.068
3. I take vitamins and other supplements that are good for my skin.	0.873	0.028	0.082	0.164	0.059
5. I frequently use functional skincare products (essence, eye cream, whitening lotion, etc.) for skincare.	0.805	0.193	0.071	0.086	0.046
23. I’ve read about makeup and put it into practice.	0.050	0.878	0.180	0.114	0.107
24. I can create a makeup style that suits me.	0.135	0.844	0.177	0.127	0.081
22. I spend a lot of time on makeup when I’m out.	0.055	0.811	0.171	0.189	–0.030
21. I tend to use color products a lot.	–0.112	0.794	0.293	0.130	0.121
25. I like to buy cosmetics and I tend to do it often.	0.241	0.714	0.245	0.226	0.071
18. I’ve ever imitated a celebrity’s outfit.	0.096	0.227	0.895	0.130	0.032
17. When I shop, I buy fashionable styles of clothing.	0.046	0.045	0.835	0.175	0.057
16. I try to wear clothes that suit me.	0.022	0.224	0.806	0.217	0.078
19. I tend to buy clothes seasonally.	0.085	0.350	0.796	0.121	0.112
20. I always wear fashion accessories (hats, bags, shoes, accessories, etc.) that complement my outfit when I dress.	0.083	0.352	0.685	0.193	0.076
6. I make a special effort to do my hair.	0.180	0.130	0.202	0.833	0.048
8. I touch my hair until I get the hairstyle I want.	0.039	0.105	0.161	0.822	–0.009
9. I often use hair dryers (blow, dryers, magic machines, etc.).	–0.053	0.169	0.224	0.783	0.068
10. I use high-quality hair products, even if they are expensive.	0.280	0.139	0.238	0.765	0.147
7. I change my style a lot, such as dyeing my hair or getting a perm.	0.129	0.184	0.006	0.726	0.040
12. When I eat, I pay attention to calories.	0.134	0.107	0.064	0.123	0.851
13. I've controlled my weight by fasting or fasting.	–0.030	0.047	0.004	–0.041	0.838
15. I have taken dietary supplements (diuretics, laxatives, weight loss pills, etc.) to lose weight.	0.082	0.081	0.101	0.076	0.796
11. I usually worry about obesity.	–0.099	0.078	0.005	0.018	0.783
14. I tend to exercise to get in shape and manage my weight.	0.232	–0.027	0.122	0.070	0.671
Eigenvalue	4.265	3.812	3.712	3.458	3.238
Explained variance (%)	17.059	15.249	14.847	13.832	12.953
Cumulative explained variance (%)	17.059	32.308	47.155	60.987	73.941
Reliability	0.938	0.910	0.913	0.881	0.855

Kaiser-Meyer-Olkin value=0.870, Bartlett’s test χ²=4,825.997 (df=300, p=0.000)..

Validity and reliability verification for self-esteem

The validity and reliability of self-esteem were analyzed, as shown in Table 3. First, the KMO value was 0.933, indicating that the sample was suitable for factor analysis. Bartlett’s test result was significant at 2321.199 (df=45, p=0.000). One factor with an eigenvalue greater than 1 was extracted, and the overall explanatory power was 71.024%. The sub-factor self-esteem accounted for 71.024%. Additionally, the reliability analysis using Cronbach’s α coefficient showed a value of 0.953, indicating highly reliable measurement items.

Table 3 . Validation and reliability assessment of self-esteem.

Question	Factor 1 (self-esteem)
2. I have a lot of good things.	0.917
7. I generally consider myself satisfied.	0.875
1. I think I’m a valuable person.	0.871
6. I think I’m okay with myself.	0.861
3. I’m a failure by and large.	0.849
5. I don’t have much to be proud of (r).	0.844
9. Sometimes I feel worthless (r).	0.818
10. There are times when I feel like I don’t have any good things about it (r).	0.803
4. I can do as much as everyone else.	0.799
8. I wish I had a little more confidence (r).	0.782
Eigenvalue	7.102
Explained variance (%)	71.024
Cumulative explained variance (%)	71.024
Reliability	0.953

Kaiser-Meyer-Olkin value=0.933, Bartlett’s test χ²=2321.199 (df=45, p=0.000)..

Descriptive statistical analysis of appearance management behavior

An analysis of appearance management behaviors among major beauty students after the COVID-19 pandemic is presented in Table 4. Overall, the results indicate that apparel management behavior (M=3.56) was the highest, followed by makeup management behavior (M=3.46), hair management behavior (M=3.41), body shape management behavior (M=3.23), and skin management behavior (M=3.07), with an average overall appearance management behavior of 3.35. When analyzed based on the respondents’ general characteristics, statistically significant differences were observed based on sex. Specifically, there were significant differences in the hair management behavior and makeup management behavior sub-factors (p<0.05). Men showed relatively higher levels of hair management behaviors than women, whereas women exhibited relatively higher levels of makeup management behaviors than men. When considering the differences by academic year, statistically significant differences were found in the skin management behavior, body shape management behavior, and makeup management behavior subfactors (p<0.01). Compared to the first year, the third and fourth years showed relatively higher levels of skin management behaviors, and compared with the second year, the first, third, and fourth years exhibited relatively higher levels of body shape management behaviors. Additionally, compared with the second and third years, the first year showed relatively higher levels of makeup management behavior. Regarding majors, there were statistically significant differences in overall appearance management behavior and sub-factors of hair management behavior, body shape management behavior, apparel management behavior, and makeup management behavior (p<0.05). Makeup majors exhibited higher levels of overall appearance management behavior and sub-factors of body shape, apparel, and makeup management behavior. In contrast, hair and makeup majors demonstrated relatively higher levels of hair management behaviors. Differences were considered statistically significant. Analysis of the data based on monthly allowance revealed statistically significant differences in overall appearance management behavior and sub-factors of skin management behavior, hair management behavior, and body shape management behavior (p<0.05). Individuals with an allowance of 500,000 won or less exhibited lower levels of overall appearance management behavior and subfactors of skin, hair, and body shape management behavior than those with an allowance of 500,000 won or more.

Table 4 . Appearance management behavior.

Category	Appearance management behavior					All
	Skin	Hair	Body shape	Apparel	Makeup
Sex
Male	3.13±1.157	3.66±0.785	3.23±1.102	3.31±0.929	2.48±1.266	3.16±0.773
Female	3.05±1.186	3.37±0.972	3.23±1.091	3.61±0.906	3.65±0.948	3.38±0.644
t-value (p)	0.358 (0.721)	2.095* (0.040)	0.015 (0.988)	–1.928 (0.055)	–5.617*** (0.000)	–1.936 (0.054)
Grade
1st-year	2.67a)±1.092	3.45±0.778	3.43b)±1.096	3.75±0.872	4.00b)±0.897	3.46±0.607
2nd-year	3.04a,b)±1.243	3.39±1.062	2.70a)±1.077	3.56±0.909	3.47a)±1.096	3.23±0.704
3rd-year	3.18b)±1.072	3.15±0.972	3.31b)±0.834	3.25±0.970	3.08a)±1.122	3.19±0.739
4th-year	3.41b)±1.127	3.50±0.952	3.58b)±0.976	3.49±0.919	3.11a)±1.059	3.42±0.647
F-value (p)	5.118** (0.002)	0.912 (0.436)	11.142*** (0.000)	2.174 (0.092)	10.156*** (0.000)	2.229 (0.085)
Major
Hair	3.07±1.142	3.70b)±0.849	3.21a,b)±1.020	3.44a,b)±0.976	3.01a)±1.309	3.29a)±0.702
Skin	2.95±1.174	3.06a)±0.926	3.04a,b)±1.207	3.35a)±0.911	3.09a)±0.930	3.10a)±0.651
Makeup	3.23±1.204	3.56b)±0.923	3.45b)±1.053	3.77b)±0.845	4.01b)±0.70	3.61b)±0.610
Nail	2.65±1.106	3.16a)±1.027	2.86a)±0.867	3.56a,b)±0.919	3.29a)±0.804	3.11a)±0.500
F-value (p)	1.828 (0.143)	6.906*** (0.000)	2.965* (0.033)	3.560* (0.015)	17.826*** (0.000)	10.566*** (0.000)
Average monthly pocket money
>100,000	3.01a,b)±1.054	3.17a)±0.613	2.75a)±0.961	3.44±0.959	3.34±0.812	3.14a)±0.625
>100,000–300,000	2.91a,b)±1.257	3.20a)±1.043	2.90a,b)±1.093	3.42±1.076	3.39±1.193	3.17a)±0.747
>300,000–500,000	2.79a)±1.278	3.32a,b)±1.062	3.27b,c)±1.130	3.61±0.871	3.69±0.858	3.34a,b)±0.660
<500,000	3.33b)±1.056	3.62b)±0.847	3.45c)±1.034	3.61±0.854	3.38±1.214	3.48b)±0.625
F-value (p)	3.437* (0.018)	3.392* (0.019)	4.770** (0.003)	0.688 (0.560)	1.402 (0.243)	3.432* (0.018)
Total	3.07±1.179	3.41±0.949	3.23±1.091	3.56±0.915	3.46±1.092	3.35±0.670

Values are presented as mean±standard deviation or n (%)..

*p<0.05, **p<0.01, ***p<0.001..

Duncan: a

Descriptive statistical analysis of self-esteem

An analysis of self-esteem among beauty majors after the COVID-19 pandemic is presented in Table 5. The mean self-esteem averaged 3.78. When analyzing differences based on the general characteristics of the respondents, statistically significant differences were observed based on academic year (p<0.01). Compared to the third year, the first-, second-, and fourth-year students showed relatively higher levels of self-esteem. However, no statistically significant differences were found based on sex, major, or monthly allowance (p>0.05).

Table 5 . Self-esteem.

Category	Mean	Standard deviation	t/F-value	p-value
Sex			–1.714	0.092
Male	3.56	0.919
Female	3.82	0.801
Grade			4.164**	0.007
1st-year	3.76b)	0.823
2nd-year	3.79b)	0.845
3rd-year	3.30a)	1.079
4th-year	3.95b)	0.639
Major			1.793	0.149
Hair	3.82	0.827
Skin	3.76	0.759
Makeup	3.86	0.843
Nail	3.42	0.898
Average monthly pocket money (won)			0.678	0.566
>100,000	3.80	0.799
>100,000–300,000	3.67	0.881
>300,000–500,000	3.74	0.803
<500,000	3.86	0.821
Total	3.78	0.825

**p<0.01..

Duncan: a

Correlation analysis

The results of the correlation analysis between appearance management behaviors and self-esteem are presented in Table 6. The analysis revealed statistically significant positive correlations between self-esteem and the subfactors of appearance management behavior: skin management behavior (r=0.378, p<0.001), hair care behavior (r=0.447, p<0.001), body shape management behavior (r=0.202, p<0.01), apparel management behavior (r=0.380, p<0.001), and makeup management behavior (r=0.380, p<0.001). In other words, all correlations between the variables showed positive and statistically significant relationships. The correlation coefficients between the variables did not exceed 0.80, indicating the absence of collinearity. The analysis confirmed discriminant validity between the concepts.

Table 6 . Correlation analysis.

Category	Appearance management behavior					Self-esteem
	Skin	Hair	Body shape	Apparel	Makeup
Skin management behavior	1
Hair management behavior	0.272***	1
Body shape management behavior	0.155*	0.166**	1
Apparel management behavior	0.182**	0.434***	0.188**	1
Makeup management behavior	0.184**	0.407***	0.187**	0.542***	1
Self-esteem	0.378***	0.447***	0.202**	0.380***	0.380***	1

*p<0.05, **p<0.01, ***p<0.001..

The impact of appearance management behavior on self-esteem in beauty major university students after COVID-19

To analyze the impact of appearance management behavior on self-esteem in beauty major university students after COVID-19, multiple regression analysis was conducted with appearance management behavior as the independent variable and self-esteem as the dependent variable. As shown in Table 7, the explanatory power of the regression model was 32.6%, and the model was statistically significant (F=23.936, p<0.001). Examining the influence of independent variables, it was found that hair care behavior (β=0.251, p<0.001), skin management behavior (β=0.248, p<0.001), makeup management behavior (β=0.147, p<0.05), and apparel management behavior (β=0.133, p<0.05) had statistically significant positive effects on self-esteem. Therefore, after COVID-19, beauty majors with higher levels of hair care, skin care, makeup management, and apparel management behaviors also tended to have higher levels of self-esteem.

Table 7 . The impact of appearance management behavior on self-esteem in beauty major university students after COVID-19.

Independent variable	Unstandardized coefficient		Standardized coefficient (β)	t	p-value
	B	Standard error
Constant	1.525	0.223		6.825	0.000
Skin management behavior	0.174	0.038		4.528***	0.000
Hair management behavior	0.218	0.053	0.251	4.128***	0.000
Body shape management behavior	0.053	0.041	0.070	1.290	0.198
Apparel management behavior	0.120	0.059	0.133	2.043*	0.042
Makeup management behavior	0.111	0.048	0.147	2.291*	0.023

R²=0.326, Adj.R²=0.313, F=23.936***, p=0.000..

*p<0.05, ***p<0.001..

This study investigated the impact of appearance management behaviors on self-esteem among university students majoring in beauty during the COVID-19 pandemic. The conclusions are as follows:

First, an analysis of university students’ appearance management behavior revealed that overall, apparel management behavior was the most prominent. Among males, hair care behavior was the most common, whereas among females, makeup management behavior took precedence. Furthermore, apparel management behavior ranked second among both males and females. This indicates that apparel management behavior significantly influences appearance management in university students, regardless of sex.

Second, in terms of differences among majors, students majoring in makeup exhibited the highest level of appearance management behavior, followed by those majoring in hair. In particular, among makeup majors, all aspects of appearance management behavior except hair care behavior were notably high. Self-esteem was ranked as follows: makeup, hair, skin, and nails. This suggests that greater interest in appearance management behavior corresponds to higher self-esteem, especially among students majoring in makeup- and hair-related fields.

Third, when examining the influence of independent variables, it was observed that hair care behavior (β=0.251, p<0.001), skin management behavior (β=0.248, p<0.001), makeup behavior (β=0.147, p<0.05), and apparel management behavior (β=0.133, p<0.05) had statistically significant positive effects on self-esteem. Therefore, among university students majoring in beauty after the COVID-19 outbreak, higher levels of self-esteem were associated with higher engagement in hair care, skin care, makeup, and apparel management behaviors. This aligns with the findings of a study by Im et al. [20], which suggested that when college students have high satisfaction with their appearance, it positively influences their self-confidence and satisfaction, acting as a positive factor in interpersonal relationships.

Fourth, according to Han [21], who studied the correlation between appearance management behaviors and self-esteem among college students before COVID-19, greater attention to appearance management behaviors was positively associated with self-esteem and interpersonal relationships. Similarly, appearance management behaviors, particularly hair management behaviors, were prominent among male students. However, before COVID-19, clothing management behaviors were most prevalent among female students, whereas after COVID-19, makeup management behaviors became predominant. This seems to be the result of changes brought about by the relaxation of COVID-19 restrictions, leading to increased outdoor activities that were previously limited by gathering restrictions and the requirement to wear masks.

This study aimed to provide foundational data to assist in promoting healthy and desirable appearance management and fostering positive self-esteem. However, caution is needed when generalizing the results of this study as it targeted university students majoring in beauty. In future research, it will be necessary to produce more meaningful results through comparisons among various age groups or non-beauty majors after COVID-19. By investigating the impact of appearance management behaviors on self-esteem among beauty majors after COVID-19, this study is anticipated to contribute to their adaptation to school life, satisfaction with appearance, and smooth interpersonal relationships within campus communities.

The authors have nothing to disclose.