| Literature DB >> 34429716 |
Benjamin Artz1, Ilker Kaya2, Ozgur Kaya2.
Abstract
Women are more likely than men to report physical and emotional exhaustion related to paid work. While this gender gap in job burnout is common in the literature, the mechanism is yet to be thoroughly understood. Our study offers a novel, and admittedly provocative, explanation for the difference in burnout between men and women. We leverage a US survey rich in job and personal information to test whether theoretically relevant factors explain the gender gap in job burnout. Our results suggest that they may not. Instead we find that workers' perspectives regarding women's role in society drive a large gender gap in job burnout. Specifically, "traditional" women are significantly more likely than men to report job burnout. Thus, providing support and resources to transform perceptions and attitudes regarding gender roles may help to reduce job-related burnout resulting from a mismatch between expectations and paid work experiences.Entities:
Keywords: Gender gap; Gender role; Job burnout; Progressive women; Unpaid caregiving and domestic work
Year: 2021 PMID: 34429716 PMCID: PMC8375289 DOI: 10.1007/s11150-021-09579-2
Source DB: PubMed Journal: Rev Econ Househ ISSN: 1569-5239
Descriptive statistics: mean (standard deviation)
| Variables and descriptions | Whole sample | Women | Men |
|---|---|---|---|
| Burnout measures (dependent variables) | |||
| Burnout composite index (equal weights) ranges from 4 if respondent answered “never” to all four component measures to 20 if respondent answered “very often” to all four component measures | 11.030 (3.440) | 11.146 (3.466) | 10.879 (3.401) |
| No energy ranges from 1 if “never” to 5 if “very often” to the question: “How often have you NOT had the energy to do things with your family or other important people in your life because of your job?” | 2.641 (1.105) | 2.660 (1.107) | 2.615 (1.102) |
| Work disrupt ranges from 1 if “never” to 5 if “very often” to the question: “How often has work kept you from doing as good a job at home as you could?” | 2.600 (1.106) | 2.610 (1.120) | 2.587 (1.087) |
| Overwhelmed ranges from 1 if “never” to 5 if “very often” to the question: “How often have you felt overwhelmed by how much you had to do at work in the last three months?” | 3.145 (1.225) | 3.224 (1.230) | 3.040 (1.211) |
| Bad mood ranges from 1 if “never” to 5 if “very often to the question: “How often have you NOT been in as good a mood as you would like to be at home because of your job?” | 2.656 (1.042) | 2.652 (1.056) | 2.637 (1.021) |
| Demographic characteristics (independent variables) | |||
| Female = 1 if respondent is a woman; 0 otherwise | 0.567 (0.496) | – | – |
| Progressive = 1 if respondent strongly disagrees with Statement A or strongly agrees with Statement Ba; 0 otherwise | 0.582 (0.496) | 0.638 (0.481) | 0.509 (0.500) |
| 2008 = 1 if NSCW 2008 wave; 0 if NSCW 2002 wave | 0.510 (0.500) | 0.498 (0.500) | 0.526 (0.499) |
| Hispanic = 1 if respondent is Hispanic; 0 otherwise | 0.059 (0.236) | 0.059 (0.236) | 0.059 (0.236) |
| Black = 1 if respondent is Black; 0 otherwise | 0.090 (0.286) | 0.108 (0.310) | 0.067 (0.250) |
| Other = 1 if respondent is another non-white ethnicity; 0 otherwise | 0.062 (0.240) | 0.057 (0.233) | 0.067 (0.250) |
| Age in years | 43.117 (11.524) | 43.486 (11.397) | 42.632 (11.674) |
| Some college = 1 if respondent has a HS but no college degree; 0 otherwise | 0.328 (0.470) | 0.331 (0.471) | 0.325 (0.469) |
| College = 1 if respondent has a college degree; 0 otherwise | 0.266 (0.442) | 0.278 (0.448) | 0.250 (0.433) |
| Post-college = 1 if respondent has a professional, masters or PhD; 0 otherwise | 0.165 (0.371) | 0.158 (0.364) | 0.174 (0.380) |
| Children = number of children under 18 that live with respondent for at least half the year | 0.802 (1.094) | 0.770 (1.061) | 0.843 (1.133) |
| Age of youngest child = age of youngest child living with respondent for at least half the year | 2.722 (5.989) | 2.857 (6.148) | 2.546 (5.771) |
| Chore time = average time in minutes spent on working days on home chores like cooking, cleaning, yard work, etc. | 142.803 (120.701) | 155.796 (121.155) | 125.773 (117.989) |
| Childcare time = average time in minutes spent on working days taking care of or doing things with their children | 79.934 (185.522) | 88.484 (219.977) | 68.728 (126.103) |
| Expected spousal income = expected annual earnings of spouse or partner, divided by 100,000 | 0.244 (0.392) | 0.280 (0.408) | 0.197 (0.365) |
| Spouse works = 1 if respondent has a spouse or partner who works for pay; 0 otherwise | 0.508 (0.500) | 0.524 (0.500) | 0.488 (0.500) |
| Spouse prefers not to work = 1 if respondent has a spouse or partner who prefers not to work for payb | 0.086 (0.280) | 0.041 (0.198) | 0.145 (0.352) |
| Spouse is unable to work = 1 if respondent has a spouse or partner who is unable to work for payc | 0.067 (0.251) | 0.054 (0.225) | 0.085 (0.279) |
| Geographic regions: | 10 regions | ||
| Job characteristics (independent variables) | |||
| Pension = 1 if workers has either defined benefit or contribution pension from employer; 0 otherwise | 0.595 (0.491) | 0.578 (0.494) | 0.619 (0.486) |
| Insurance = 1 if employer offers health insurance; 0 otherwise | 0.869 (0.337) | 0.850 (0.358) | 0.895 (0.307) |
| Vacation = 1 if employer provides vacation days; 0 otherwise | 0.812 (0.391) | 0.786 (0.410) | 0.845 (0.362) |
| PTO = 1 if employer provides paid-time-off for sickness or other needs; 0 otherwise | 0.699 (0.459) | 0.710 (0.454) | 0.685 (0.465) |
| Easy time off = 1 if respondent finds it to be easy to ask for time off when needed; 0 otherwise | 0.624 (0.484) | 0.597 (0.491) | 0.660 (0.474) |
| Flexible time = 1 if respondent can choose starting and ending hours; 0 otherwise | 0.457 (0.498) | 0.439 (0.496) | 0.482 (0.500) |
| Union = 1 if respondent is a member of a labor union; 0 otherwise | 0.193 (0.395) | 0.180 (0.384) | 0.210 (0.407) |
| Tenure with employer in years | 8.592 (8.723) | 8.157 (8.304) | 9.161 (9.215) |
| Usual weekly work hours | 37.108 (8.318) | 35.678 (8.951) | 38.982 (6.980) |
| Hourly wage | 33.074 (77.724) | 27.836 (60.086) | 39.939 (95.641) |
| Private sector = 1 if respondent’s job is at a for-profit employer; 0 otherwise | 0.624 (0.484) | 0.555 (0.497) | 0.714 (0.452) |
| Risk of layoff = 1 if respondent is “very likely” or “somewhat likely” that during the next couple of years they will lose their job and have to look for a job with another employer. | 0.256 (0.437) | 0.240 (0.427) | 0.279 (0.448) |
| High female proportion = 1 if the proportion of respondents working in each unique industry and occupation intersection is greater than 50% | 0.665 (0.472) | 0.855 (0.352) | 0.415 (0.493) |
| Industries: | 12 groups | ||
| Occupations: | 14 groups | ||
| Observations | 4173 | 2367 | 1806 |
aStatement A: It is much better for everyone involved if the man earns the money and the woman takes care of the home and children
aStatement B: A mother who works outside the home can have just as good a relationship with her children as a mother who does not work
bPreferential reasons include taking care of children or other dependents, doing volunteer work, caring for household or pursuing personal interests, or is retired
cInability to work reasons include inability to find a job, is in school or training, cannot afford to work outside the home given dependent care expenses, or is ill, injured or disabled
OLS burnout composite regressions (2002 & 2008 NSCW)
| Whole sample | Whole sample | Women | Men | Whole sample | |
|---|---|---|---|---|---|
| (1) | (2) | (3) | (4) | (5) | |
| Female | 0.491*** (3.363) | 0.553*** (3.774) | 2.962 (1.102) | ||
| Progressive | −0.698*** (−5.353) | −1.138*** (−7.051) | −0.309 (−1.620) | −0.309 (−1.620) | |
| 2008 cohort | 0.290* (1.862) | 0.321** (2.056) | 0.210 (1.011) | 0.342 (1.535) | 0.342 (1.535) |
| Hispanic | −0.161 (−0.541) | −0.097 (−0.324) | 0.150 (0.418) | −0.371 (−0.831) | −0.371 (−0.831) |
| Black | −0.314 (−1.282) | −0.248 (−1.016) | −0.388 (−1.426) | −0.166 (−0.415) | −0.166 (−0.415) |
| Other race | −0.290 (−1.108) | −0.297 (−1.129) | −0.077 (−0.217) | −0.524 (−1.428) | −0.524 (−1.428) |
| Age | 0.079** (1.973) | 0.073* (1.841) | −0.001 (−0.017) | 0.148*** (2.590) | 0.148*** (2.590) |
| Age squared | −0.001*** (−2.650) | −0.001*** (−2.582) | −2.70 × 10−4 (−0.408) | −0.002*** (−3.293) | −0.002*** (−3.293) |
| Some college | 0.049 (0.301) | 0.060 (0.365) | 0.117 (0.550) | −0.006 (−0.028) | −0.006 (−0.028) |
| College degree | 0.370* (1.954) | 0.379** (2.019) | 0.360 (1.513) | 0.425 (1.488) | 0.425 (1.488) |
| Advanced degree | 0.675*** (2.957) | 0.719*** (3.175) | 1.053*** (3.491) | 0.412 (1.257) | 0.412 (1.257) |
| Children | 0.127 (1.099) | 0.099 (0.847) | 0.104 (0.798) | 0.142 (0.835) | 0.142 (0.835) |
| Age of youngest child | 0.000 (0.005) | −0.002 (−0.134) | 0.005 (0.377) | −0.009 (−0.479) | −0.009 (−0.479) |
| Log chore time | 0.047 (0.928) | 0.044 (0.871) | 0.126 (1.640) | −0.006 (−0.092) | −0.006 (−0.092) |
| Log childcare time | −0.036 (−0.865) | −0.029 (−0.682) | −0.031 (−0.647) | −0.035 (−0.529) | −0.035 (−0.529) |
| Expected spousal income | −0.180 (−0.983) | −0.119 (−0.653) | −0.147 (−0.606) | −0.081 (−0.320) | −0.081 (−0.320) |
| Spouse works | 0.207 (1.249) | 0.161 (0.972) | 0.044 (0.210) | 0.306 (1.217) | 0.306 (1.217) |
| Spouse prefers not to work | 0.404 (1.297) | 0.336 (1.041) | 0.310 (0.752) | 0.413 (0.973) | 0.413 (0.973) |
| Spouse is unable to work | 0.802*** (2.770) | 0.754*** (2.583) | 0.147 (0.394) | 1.382*** (3.367) | 1.382*** (3.367) |
| Pension | −0.130 (−0.891) | −0.107 (−0.739) | −0.027 (−0.140) | −0.172 (−0.825) | −0.172 (−0.825) |
| Health insurance | −0.271 (−1.146) | −0.284 (−1.186) | −0.103 (−0.369) | −0.549 (−1.462) | −0.549 (−1.462) |
| Vacation days | 0.130 (0.663) | 0.131 (0.665) | 0.388* (1.668) | −0.154 (−0.488) | −0.154 (−0.488) |
| Paid time off | −0.217 (−1.371) | −0.181 (−1.132) | −0.014 (−0.066) | −0.448** (−2.029) | −0.448** (−2.029) |
| Easy time off | −2.018*** (−14.811) | −2.006*** (−14.698) | −2.025*** (−12.267) | −1.990*** (−9.520) | −1.990*** (−9.520) |
| Flex time | −0.311** (−2.424) | −0.297** (−2.315) | −0.444*** (−2.849) | −0.143 (−0.725) | −0.143 (−0.725) |
| Union member | −0.145 (−0.812) | −0.147 (−0.829) | 0.110 (0.493) | −0.380 (−1.484) | −0.380 (−1.484) |
| Tenure | 0.042* (1.837) | 0.037 (1.599) | 0.003 (0.091) | 0.067** (1.981) | 0.067** (1.981) |
| Tenure squared | −0.001 (−1.226) | −0.001 (−1.060) | −1.65 × 10−4 (−0.175) | −0.001 (−1.219) | −0.001 (−1.219) |
| Usual weekly hours | 0.058*** (6.496) | 0.060*** (6.637) | 0.065*** (5.772) | 0.049*** (3.465) | 0.049*** (3.465) |
| Log hourly wage | 0.084 (0.847) | 0.087 (0.871) | 0.183 (1.327) | 0.076 (0.542) | 0.076 (0.542) |
| Private sector | −0.279 (−1.541) | −0.302* (−1.669) | −0.037 (−0.178) | −0.737** (−2.435) | −0.737** (−2.435) |
| Risk of layoff | 1.264*** (8.621) | 1.249*** (8.522) | 1.152*** (6.085) | 1.327*** (6.155) | 1.327*** (6.155) |
| High female proportion | 0.353 (1.550) | 0.343 (1.507) | 0.258 (0.728) | 0.406 (1.282) | 0.406 (1.282) |
| Female × progressive | −0.829*** (−3.317) | ||||
| Female × age | −0.149* (−1.893) | ||||
| Female × age squared | 0.002** (2.081) | ||||
| Female × spouse is unable to work | −1.235** (−2.230) | ||||
| Female × private sector | 0.700* (1.906) | ||||
| Occupations (14) | Yes | Yes | Yes | Yes | |
| Industries (12) | Yes | Yes | Yes | Yes | |
| Regions (10) | Yes | Yes | Yes | Yes | |
| Constant | 8.819*** (5.660) | 10.950*** (7.193) | 7.988*** (3.603) | 7.988*** (3.604) | |
| Observations | 4173 | 2367 | 1806 | 4173 | |
| R-squared | 0.190 | 0.220 | 0.208 | 0.215 |
Each column incorporates survey weights in the estimations. Heteroskedasticity robust standard errors are used throughout. T-statistics are in parentheses. Asterisk, double asterisks and triple asterisks reflect statistical significance at the 10, 5 and 1% levels respectively. In the interest of brevity, column (5) only reports the statistically significant interaction terms.
Burnout oaxaca-blinder decomposition
| Gender gap | Explained | Unexplained | |
|---|---|---|---|
| (1) | (2) | (3) | |
| Whole sample | 0.255* (1.923) | −0.297*** (−2.856) | 0.553*** (3.801) |
| Progressive | 0.051 (0281) | −0.293** (−2.025) | 0.344* (1.852) |
| Not progressive | 0.717*** (3.785) | −0.137 (−0.855) | 0.854*** (3.904) |
| Traditional-Progressive gap | Explained | Unexplained | |
| Womena | 1.081*** (6.237) | −0.057 (−0.619) | 1.138*** (7.184) |
t-statistics are in parentheses; asterisk, double asterisks and triple asterisks reflect statistical significance at the 10, 5 and 1% levels, respectively. We used the Oaxaca program with the pooled option (Jann, 2008) in Stata 16.0 for this analysis
athe gap is between progressive and non-progressive women. The gap in column (1) indicates that non-progressive women exhibit 1.081 more burnout points than progressive women
| No energy | Work disrupts | Overwhelmed | Bad mood | |
|---|---|---|---|---|
| (1) | (2) | (3) | (4) | |
| Female | 0.129*** (2639) {0.015} | 0.124** (2.478) {0.014} | 0.155*** (3.269) {0.038} | 0.125** (2.530) {0.014} |
| Observations | 4173 | 4173 | 4173 | 4173 |
All Table 2 Column 1 covariates are also included in each column’s estimations. Each column incorporates survey weights in the estimations. Heteroskedasticity robust standard errors are used throughout. T-statistics are in parentheses
Asterisk, double asterisks and triple asterisks reflect statistical significance at the 10, 5 and 1% levels respectively. Marginal effects are in brackets
| No energy | Work disrupts | Over-whelmed | Bad mood | Burnout composite | ||
|---|---|---|---|---|---|---|
| (1) | (2) | (3) | (4) | (5) | (6) | |
| Female | −0.011 (−0.014) | 1.999** (2.400) | 0.130 (0.123) | 0.845 (1.072) | 2.984 (1.107) | 3.058 (1.147) |
| Progressive | −0.184*** (−2.814) | −0.052 (−0.798) | −0.017 (−0.271) | −0.056 (−0.940) | ||
| Female * progressive | −0.144* (−1.708) | −0.244*** (−2.877) | −0.214** (−2.416) | −0.228*** (−2.878) | ||
| More progressive | −0.234 (−1.145) | |||||
| Female * more progressive | −0.869*** (−3.361) | |||||
| Most progressive | −0.151 (−0.588) | |||||
| Female * most progressive | −0.990*** (−3.220) | |||||
| Constant | 2.093*** (3.332) | 1.233** (2.028) | 2.533*** (2.991) | 2.129*** (3.798) | 7.822*** (3.530) | 7.665*** (3.518) |
| Observations | 4173 | 4173 | 4173 | 4173 | 4173 | 4173 |
| R-squared | 0.169 | 0.156 | 0.139 | 0.160 | 0.214 | 0.213 |
All Table 2 Column 4 covariates and interactions are also included in each column’s estimations. Each column incorporates survey weights in the estimations. Heteroskedasticity robust standard errors are used throughout. T-statistics are in parentheses
Asterisk, double asterisks and triple asterisks reflect statistical significance at the 10, 5 and 1% levels respectively
| Progressive | Not progressive | More progressive | Not more progressive | Most progressive | Not most progressive | |
|---|---|---|---|---|---|---|
| (1) | (2) | (3) | (4) | (5) | (6) | |
| Female | 0.344* (1.853) | 0.854*** (3.785) | 0.074 (0.339) | 0.883*** (4.490) | −0.038 (−0.141) | 0.827*** (4.874) |
| 2008 cohort | 0.243 (1.148) | 0.312 (1.394) | 0.277 (1.099) | 0.327* (1.695) | −0.107 (−0.327) | 0.411** (2.441) |
| Hispanic | −0.083 (−0.217) | −0.056 (−0.143) | −0.664* (−1.668) | 0.139 (0.359) | −1.360*** (−2.953) | 0.313 (0.925) |
| Black | −0.370 (−1.234) | −0.298 (−0.792) | −0.270 (−0.769) | −0.450 (−1.483) | −0.330 (−0.760) | −0.440 (−1.634) |
| Other race | −0.179 (−0.507) | −0.444 (−1.188) | 0.278 (0.672) | −0.603* (−1.867) | 0.406 (0.816) | −0.424 (−1.446) |
| Age | 0.022 (0.405) | 0.177*** (3.165) | 0.079 (1.252) | 0.092* (1.843) | 0.164** (2.077) | 0.055 (1.238) |
| Age squared | −0.001 (−0.947) | −0.002*** (−3.670) | −0.001* (−1.730) | −0.001** (−2.416) | −0.002** (−2.382) | −0.001* (−1.956) |
| Some college | 0.158 (0.722) | −0.017 (−0.074) | −0.077 (−0.298) | 0.201 (1.013) | −0.169 (−0.481) | 0.133 (0.750) |
| College degree | 0.670*** (2.695) | 0.069 (0.247) | 0.482 (1.631) | 0.392 (1.632) | −0.029 (−0.076) | 0.531** (2.493) |
| Advanced degree | 0.981*** (3.271) | 0.317 (0.962) | 0.821** (2.400) | 0.705** (2.399) | 0.267 (0.587) | 0.885*** (3.442) |
| Children | 0.096 (0.548) | 0.106 (0.825) | 0.151 (0.612) | 0.095 (0.831) | 0.200 (0.631) | 0.077 (0.712) |
| Age of youngest | 0.008 (0.479) | −0.011 (−0.648) | 0.012 (0.649) | −0.007 (−0.504) | 0.008 (0.331) | −0.002 (−0.169) |
| Log chore time | 0.084 (1.302) | −0.004 (−0.053) | 0.093 (1.192) | 0.022 (0.355) | 0.204* (1.929) | 0.003 (0.060) |
| Log childcare time | −0.006 (−0.100) | −0.056 (−1.057) | −0.032 (−0.406) | −0.041 (−0.900) | −0.082 (−0.823) | −0.015 (−0.360) |
| Exp. spousal inc. | −0.122 (−0.580) | −0.217 (−0.566) | −0.120 (−0.571) | −0.253 (−0.838) | 0.025 (0.112) | −0.283 (−1.097) |
| Spouse works | 0.018 (0.088) | 0.330 (1.257) | 0.055 (0.236) | 0.228 (1.013) | −0.080 (−0.278) | 0.238 (1.212) |
| Spouse prefers not | 0.407 (0.775) | 0.322 (0.992) | 0.493 (1.202) | 0.296 (0.820) | 0.749 (1.373) | 0.316 (0.940) |
| Spouse is unable | 0.533 (1.237) | 0.841** (2.391) | 0.235 (0.467) | 0.945*** (2.765) | 0.052 (0.078) | 0.975*** (3.210) |
| Pension | −0.153 (−0.792) | −0.054 (−0.257) | −0.182 (−0.801) | −0.101 (−0.558) | −0.027 (−0.089) | −0.155 (−0.974) |
| Health insurance | −0.812** (−2.557) | 0.370 (1.089) | −0.368 (−1.010) | −0.167 (−0.584) | −0.541 (−1.154) | −0.158 (−0.614) |
| Vacation days | 0.066 (0.251) | 0.235 (0.853) | −0.051 (−0.165) | 0.259 (1.062) | −0.446 (−1.110) | 0.325 (1.506) |
| Paid time off | −0.332 (−1.576) | 0.009 (0.041) | −0.181 (−0.744) | −0.172 (−0.843) | 0.063 (0.194) | −0.255 (−1.449) |
| Easy time off | −1.810*** (−9.957) | −2.119*** (−10.885) | −1.935*** (−9.445) | −1.981*** (−11.241) | −2.196*** (−8.597) | −1.918*** (−12.448) |
| Flex time | −0.319* (−1.932) | −0.209 (−1.110) | −0.292 (−1.528) | −0.235 (−1.449) | −0.552** (−2.268) | −0.265* (−1.862) |
| Union member | −0.197 (−0.828) | 0.044 (0.176) | −0.248 (−0.887) | −0.075 (−0.337) | −0.606 (−1.573) | 0.020 (0.104) |
| Tenure | 0.054* (1.660) | 0.008 (0.262) | 0.030 (0.752) | 0.038 (1.385) | 0.064 (1.231) | 0.038 (1.527) |
| Tenure squared | −0.001 (−1.255) | 4.45 × 10−5 (0.044) | −3.98 × 10−4 (−0.312) | −0.001 (−0.981) | −0.002 (−1.071) | −0.001 (−0.864) |
| Usual weekly hours | 0.071*** (5.939) | 0.052*** (3.859) | 0.064*** (4.880) | 0.054*** (4.692) | 0.060*** (3.309) | 0.057*** (5.694) |
| Log hourly wage | 0.246* (1.853) | −0.097 (−0.681) | 0.268* (1.840) | −0.049 (−0.364) | 0.377* (1.747) | 0.011 (0.098) |
| Private sector | −0.393 (−1.575) | −0.162 (−0.653) | −0.724** (−2.358) | −0.006 (−0.029) | −0.854** (−2.137) | −0.114 (−0.602) |
| Risk of layoff | 1.277*** (6.446) | 1.156*** (5.613) | 1.283*** (5.724) | 1.213*** (6.523) | 1.337*** (4.647) | 1.208*** (7.330) |
| High female prop. | 0.174 (0.600) | 0.564 (1.559) | 0.018 (0.056) | 0.605* (1.907) | −0.182 (−0.469) | 0.467* (1.717) |
| Occupations (14) | Yes | Yes | Yes | Yes | Yes | Yes |
| Industries (12) | Yes | Yes | Yes | Yes | Yes | Yes |
| Regions (10) | Yes | Yes | Yes | Yes | Yes | Yes |
| Constant | 8.773*** (3.958) | 6.212*** (3.404) | 8.084*** (3.063) | 7.768*** (4.985) | 3.655 (1.353) | 9.602*** (6.027) |
| Observations | 2428 | 1745 | 1729 | 2444 | 1037 | 3136 |
| R-squared | 0.185 | 0.228 | 0.217 | 0.196 | 0.256 | 0.189 |
The groups labeled “Not” in the above categories reflect the portion of the sample that does not belong to that category. The “Not more progressive” segment, for example, represents the portion of the sample that is not “more progressive”. Each column incorporates survey weights in the estimations. Heteroskedasticity robust standard errors are used throughout. T-statistics are in parentheses
Asterisk, double asterisks and triple asterisks reflect statistical significance at the 10, 5 and 1% levels respectively