About

Ellis Monk is a Professor of Sociology at Harvard University and a Visiting Faculty Researcher at Google. His research encompasses a broad range of topics including race and ethnicity in comparative perspective, colorism, health, and the intersection of race, ethnicity, and technology, particularly in areas such as artificial intelligence, machine learning, and computer vision. Additionally, his work engages with the sociology of the body, social psychology, and sociological theory. Professor Monk has made significant contributions to the study of colorism, notably through his research on colorism in AI and the development of the Monk Skin Tone Scale. He is a recipient of the NIH Director’s New Innovator Award (2022-2027), which supports his research on the relationship between skin tone and pulse oximetry. His academic and research activities are based at Harvard University, with additional affiliation at Google AI.

Research topics

• Sociology
• Social Science
• Gender studies
• Demography
• Political Science
• Demographic economics
• Psychology
• Economics
• Development economics
• Epistemology
• Biology
• Social psychology
• Law
• Positive economics

Selected publications

• Beauty, Race/Ethnicity, and Gender Inequalities

  Handbooks of sociology and social research · 2026-01-01

  book-chapterOpen access1st authorCorresponding

  Abstract The social scientific study of beauty convincingly documents significant and substantial inequalities associated with perceptions of who is (and is not) beautiful. Much of this research shows, for instance, that those perceived to be beautiful are more likely to be better educated, employed, earn higher wages, marry those of higher social status, and even experience relative leniency in the criminal justice system. Some of these studies find that the advantages of being perceived as beautiful are similar to or even larger than measures of actual ability. Moreover, studies even document that beauty premia begin to manifest in childhood through differences in parental investment and affect, in addition to favorable treatment from teachers and peers. All told, then, it is quite clear that beauty matters for social inequality and stratification. What is less clear, however, is how race intersects with beauty and shapes patterns of social inequality and stratification. This chapter synthesizes literature across the social sciences on how race (and gender) intersects with beauty, powerfully influencing who gets what and how much in societies all over the world. In so doing, it both provides a view of the current state of our knowledge and highlights opportunities for much needed future research.

  PublisherOA PDFDOI

• Towards achieving even distributions of participant skin tones when verifying pulse oximeter performance

  Research Square · 2025-10-08

  preprintOpen accessSenior author
  PublisherOA PDFDOI

• Comparison of objective and subjective tools for assessing skin pigmentation diversity: implications for pulse oximeter validation (Conference Presentation)

  2025-03-20

  article
  PublisherDOI

• Comparison of methods for characterizing skin pigment diversity in research cohorts

  medRxiv · 2025-02-25 · 6 citations

  preprintOpen access

  Background: Some pulse oximeters perform worse in people with darker skin, and this may be due to inadequate diversity of skin pigment in device development study cohorts. Guidance is needed to accurately and equitably characterize skin pigment to ensure diversity in research cohorts. We tested multiple methods for characterizing skin pigment to assess comparability and impact on cohort diversity. Objectives: Assess reliability and comparability of common skin pigment measurement methodsCompare findings from different anatomical sitesDemonstrate that pigment cannot be assumed from US National Institutes for Health (NIH) race categories. Methods: We used three subjective methods (perceived Fitzpatrick pFP, Monk Skin Tone MST and Von Luschan VL) and two objective methods (Konica Minolta CM-700d spectrophotometer and Delfin Skin Color Catch DSCC colorimeter) for individual typology angle (ITA), across multiple measurement sites in adults. We calculated ΔE to estimate operator perceptibility thresholds for subjective methods and to determine reproducibility for objective methods. We used each method to categorize participants as 'light, medium, or dark' and compared the impact of method selection on cohort diversity. Results: We studied 789 participants, with 33,856 assessments. The MST had the widest luminosity range, and VL had the least discernible adjacent categories. With 'dark' defined as ITA <-30°, 14% of participants were categorized 'dark' as compared to 26% by pFP or 16% by MST. Approximately half of the 'dark' cohort had an ITA <-50°. With an ITA threshold <-50°, only 7% of the cohort was categorized as 'dark.' When 'Black or African American' self-identification was used to define 'dark', 23% of the cohort was categorized as such. Each self-assigned NIH race category included a wide range of ITA and subjective scale categories. Both ITA and L* from the KM-700d and DSCC demonstrated strong correlation (ρ > 0.7). Conclusion: Common methods for skin pigment characterization, especially the use of race or subjective scales, have significant limitations. When applied to the same cohort, different methods yield significantly different results, and some may overestimate diversity. Previously published ITA thresholds for defining 'dark' skin are too light and lead to underrepresentation of people with darker skin.

  PublisherOA PDFDOI

• Experiences of In-Group and Out-Group Skin Tone Discrimination and Their Associations with Incident Cardiovascular Disease Among African American Adults in the Jackson Heart Study

  Journal of Racial and Ethnic Health Disparities · 2025-08-07 · 1 citations

  articleOpen access

  BACKGROUND: African American adults face an elevated risk of cardiovascular disease (CVD) compared to other racial and/or ethnic groups in the USA. Although discrimination has been linked to this disparity, the relationship between skin tone discrimination and CVD incidence remains scarce. This study investigated the associations of in-group discrimination (from African American individuals) and out-group skin tone discrimination (from White individuals) with incident CVD and whether these associations differed by sex and optimism. METHODS: This study analyzed data from 3519 African American participants (aged 21-95 years) in the Jackson Heart Study from 2000 to 2016. Cox Proportional Hazards regression assessed associations between skin tone discrimination and CVD (including stroke and coronary heart disease (CHD)). Each CVD component, along with heart failure (HF), was also analyzed separately. Models adjusting for sociodemographic characteristics, health behaviors, and CVD risk factors estimated hazard ratios (HR) and 95% confidence intervals (CI). Interaction terms were included in the fully adjusted models to assess the moderating roles of sex and optimism. RESULTS: Over the 16-year follow-up, 8.0% of participants developed CVD, 3.9% developed stroke, 4.9% developed CHD, and 7.3% developed HF. Participants who reported that Black individuals treated them better than other Black individuals because of their skin tone had an increased risk of CVD (HR 1.33, 95% CI 0.95-1.83). Out-group skin tone discrimination, whether better or worse treatment, was associated with a higher incidence of CHD (HRs ranged from 1.23 to 1.43), although CIs were wide. These associations did not vary by sex. Optimism moderated the association between out-group skin tone discrimination and HF, such that those who reported worse treatment and had the highest level of optimism had the greatest risk of HF. Optimism did not moderate the associations between in-group skin tone discrimination and the CVD outcomes. CONCLUSIONS: These findings highlight the differential impact of in-group and out-group skin tone discrimination on cardiovascular health. Better in-group treatment was marginally linked to a higher CVD risk, while out-group skin tone discrimination, whether better or worse treatment, marginally increased CHD risk. Skin tone discrimination may therefore be a unique risk factor for CVD for African American individuals.

  PublisherOA PDFDOI

• EquiOx: A Prospective study of pulse oximeter bias and skin pigmentation in critically-ill adults

  medRxiv · 2025-10-07 · 1 citations

  preprintOpen access

  Abstract Rationale Pulse oximeter performance may vary by skin pigmentation, but most data are retrospective with key limitations. Objective To quantify pulse oximeter bias [mean difference between pulse oximeter oxygen saturation (SpO 2 ) and arterial blood functional oxygen saturation (SaO 2 )], and average root mean square error (A RMS ) and estimate adjusted effects of skin pigment on bias or A RMS in critically-ill adults Methods Prospective single-center study of 631 ICU patients (2022–2024) directly observed SpO and SaO pairs. Skin pigment was assessed using the subjective Monk Skin Tone Scale and objective spectrophotometry measurement (Individual Typology Angle [ITA]). Adjusted effects were estimated with targeted maximum likelihood estimation. Main Results Among 1,760 paired measurements from 631 critically-ill adults, median SaO 2 was 98% (IQR 96%, 99%) with 40 episodes of stable hypoxemia (SpO 2 &lt;90%). SpO 2 systematically underestimated SaO 2 [median bias= −1.70 IQR (−2.84, −0.50)]. Bias was less negative in patients with darker skin (ITA &lt;-30°) [−1.05 (−2.44, −0.10)] vs lighter skin (ITA &gt;30°) [−2.01 (−3.34, −1.00)] and remained significantly different in adjusted analyses. A RMS was 3.87 (95% CI 3.25, 4.53) overall and 4.49 (95% CI 2.63, 7.07) in patients with darker skin. Ear probes performed worse than finger probes [bias: −2.20 vs. −1.60; A RMS : 4.90 vs. 2.70]. Conclusions In this large ICU cohort, hypoxemia was rare, pulse oximeters systematically underestimated SaO, performance varied by skin pigment and probe site. Bias was less negative in patients with darker skin. Pulse oximeter inaccuracies in ICU patients may be more substantial than clinicians recognize. Key Points Question Does pulse oximeter bias in critically-ill adults differ by skin pigmentation? Findings In this prospective, single-center study of 631 critically-ill adults, oximeter mean bias was negative for all patients but relatively less negative for patients with darker pigment. Bias variation by pigment was nonlinear and larger in ear than finger probes. Meaning Pulse oximeter bias varies with skin pigmentation and may not always be positive in patients with darker pigmentation. Pulse oximeter inaccuracy may be larger than clinicians appreciate. Additional studies with multiple oximeter brands and more stable hypoxemia are needed to further understand bias variation with skin pigment.

  PublisherOA PDFDOI

• Pulse Oximeter Performance Across Varied Skin Pigment: A Comparative Analysis of Current and Emerging Regulatory Standards

  American Journal of Respiratory and Critical Care Medicine · 2025-05-01

  article

  Abstract Rationale: The performance of pulse oximeters varies and is often less accurate in patients with darker skin. The International Organization for Standardization (ISO) and US Food and Drug Administration (FDA) are updating standards and guidance for pulse oximeters, in part to reduce performance disparities linked to skin pigment. We tested commonly used pulse oximeters with current and anticipated FDA and ISO regulatory guidance and standards. We hypothesized more stringent anticipated regulations would result in more diverse study cohorts and fewer devices ‘passing’ compared to existing regulations. Methods: We used a controlled desaturation protocol to test 28 pulse oximeters across arterial oxygen saturations (SaO2) between 70-100% in healthy adults. We did not warm most participants’ hands during the study to promote varied pulsatility amplitudes (i.e., perfusion index). We assessed skin pigmentation with the Monk Skin Tone (MST) scale and used the Konica Minolta CM-700d spectrophotometer to calculate individual typography angle (ITA) at the subjects’ foreheads. Participants were divided into light, medium, and dark pigment groups using MST and ITA values. We calculated the root mean square difference (Arms), mean bias, and absolute differential bias, along with 95% confidence intervals for each device cohort. Results: We conducted 305 desaturation studies using the 28 devices to ensure each device had &amp;gt;500 paired SaO2-SpO2 readings and ≥24 subjects with six darkly pigmented subjects. In our testing, 18 of 28 devices met an Arms of &amp;lt;3%. All but one of the 18 devices also passed the additional anticipated performance recommendations of ITA-derived differential bias. Our analysis found more positive bias in eight oximeters for participants in the dark skin pigmentation category relative to participants with lighter skin pigmentation. Bootstrapping analysis of our data to create 100 simulated cohorts of 10 subjects (with two darkly pigmented subjects) vs 100 cohorts of 24 subjects (with at least six darkly pigmented subjects) revealed that when using current ISO guidelines (Arms &amp;lt;4%) for 10 subject cohorts, 18 devices passed for all simulated cohorts, while only 13 devices passed with an Arms &amp;lt;3% for all simulated cohorts of 24 subjects. Conclusion: Pulse oximeters show variable performance across manufacturers and models, with some of the devices we tested showing more positive bias in people with darker skin pigmentation. Anticipated updates to regulatory frameworks are likely to raise the bar for performance standards, but whether this will translate into improved real-world performance or reduced health disparities is yet to be determined.

  PublisherDOI

• 0699 Characterization of skin tone in Uganda using subjective and objective methods

  Journal of Investigative Dermatology · 2025-07-21

  article
  PublisherDOI

• Comparison of methods for characterizing skin pigment diversity in research cohorts

  British Journal of Dermatology · 2025-10-09 · 1 citations

  articleOpen access

  BACKGROUND: Some pulse oximeters perform worse in people with darker skin, and this may be due to inadequate diversity of skin pigment in device development study cohorts. Guidance is needed to accurately and equitably characterize skin pigment to ensure diversity in research cohorts. We tested multiple methods for characterizing skin pigment to assess comparability and impact on cohort diversity. OBJECTIVES: The objectives of this study were to assess reliability and comparability of common skin pigment measurement methods, compare findings from different anatomical sites and demonstrate that pigment cannot be assumed from US National Institutes for Health (NIH) race categories. METHODS: We used three subjective methods [perceived Fitzpatrick (pFP) scale, Monk Skin Tone (MST) scale and Von Luschan (VL) scale] and two objective methods [Konica Minolta CM-700d spectrophotometer and Delfin Skin Color Catch (DSCC) colorimeter] for individual typology angle (ITA) across multiple measurement sites in adults. We calculated ΔE to estimate operator perceptibility thresholds for subjective methods and to determine reproducibility for objective methods. We used each method to categorize participants as 'light, medium or dark' and compared the impact of method selection on cohort diversity. RESULTS: We studied 789 participants, with 33 856 assessments. The MST had the widest luminosity range, and the VL scale had the least discernible adjacent categories. With 'dark' defined as ITA < -30°, 14% of participants were categorized 'dark' as compared with 26% by pFP or 16% by MST. Approximately half of the 'dark' cohort had an ITA < -50°. With an ITA threshold < -50°, only 7% of the cohort was categorized as 'dark'. When 'Black or African American' self-identification was used to define 'dark', 23% of the cohort was categorized as such. Each self-assigned NIH race category included a wide range of ITA and subjective scale categories. Both ITA and L* from the KM-700d and DSCC demonstrated strong correlation (ρ > 0.7). CONCLUSIONS: Common methods for skin pigment characterization, especially the use of race or subjective scales, have significant limitations. When applied to the same cohort, different methods yield significantly different results and some may overestimate diversity. Previously published ITA thresholds for defining 'dark' skin are too light and lead to under-representation of people with darker skin.

  PublisherOA PDFDOI

• Experiences of In-Group and Out-Group Skin Tone Discrimination and Their Associations with Incident Cardiovascular Disease Among African American Adults in the Jackson Heart Study

  UNC Libraries · 2025-08-14

  articleOpen access
  PublisherDOI

Frequent coauthors

• Wim Verkruysse

  Philips (India)

  9 shared

• Michael Jaffe

  Philips (Netherlands)

  9 shared

• Michael S. Lipnick

  San Francisco General Hospital

  4 shared

• Olubunmi Okunlola

  New York University

  3 shared

• Leonid Shmuylovich

  Washington University in St. Louis

  3 shared

• Isabella Auchus

  University of California, San Francisco

  3 shared

• Gregory Leeb

  University of California, San Francisco

  3 shared

• Tyler J. Law

  University of California, San Francisco

  3 shared