Abstract
Historically, researchers and policy planners have selected a single indicator to measure trends in social inequalities. A more rigorous approach is to review the literature and data, select appropriate inequality measures to address the research question, compute results from various indices, and graphically compare resulting trends. The Health Disparities Calculator (HD*Calc, version 1.2.4; National Cancer Institute, Bethesda, MD) computes results from different indices and graphically displays them, making an arduous task easier, more transparent, and more accessible.
Health disparities are complex social phenomena. Economists and other social scientists have developed many indices to measure trends in inequality. As noted by Sen and Foster, “If a concept has some basic ambiguity, then a precise representation of that ambiguous concept must preserve that ambiguity . . . for descriptive accuracy in inequality measurement. . . .”1(p121) No single measure exists that reflects the complexities of inequality. Instead, there is a range of measures for different aspects of the concept. World Bank Chief Economist Martin Ravaillion noted, “There is no economic theory that tells us that inequality is relative, not absolute. Rather, they are two different concepts.”2(p27) HD*Calc facilitates the exploration of a variety of disparity indices.
BACKGROUND AND DEVELOPMENT OF THE HEALTH DISPARITIES CALCULATOR
A Healthy People 2010 goal was to eliminate health disparities.3 This goal, which was expanded in Healthy People 20204 to “achieve health equity, eliminate disparities, and improve the health of all groups,” raised the dilemma: how can we define and measure disparities? The National Center for Health Statistics developed the Index of Disparity as the official disparities measure for Healthy People 2000.5 Scientists have developed many indices, each with different measurement characteristics, to capture the complexity of disparities.
In a parallel effort, the National Cancer Institute established a contract to produce 2 monographs. The first reviewed and compared the various indices, and concluded that a suite of measures is needed to yield a scientifically rigorous representation of health disparities.6 The second monograph compared multiple indices, employing cancer control data and interpreting the results.7 HD*Calc was designed so that public health practitioners and researchers can examine and compare different disparities indices using their own data.
After reviewing the literature and identifying a wide range of summary indices used to measure trends in disparities, the National Cancer Institute–led team selected the most commonly used indices in public health and added others with special features to include in the first monograph. For example, the concentration indices calculate not only changes in trends, but also which group is favored by change. A key recommendation of the first monograph is to compare different summary measures on a single data set; this approach would help researchers better capture the nuances of their data. Examples of this were presented in the second monograph. However, computing multiple summary measures is arduous and it seemed unlikely that researchers would perform this series of tasks. To make the process more manageable, 11 summary measures were programmed into a new online tool, HD*Calc. HD*Calc summary measures are not unique to HD*Calc. Other than using a consistent approach to computing standard errors (Taylor Series), the HD*Calc tool presents and calculates all 11 indices as originally published. HD*Calc can be used with Joinpoint, version 4.1.0 (http://surveillance.cancer.gov/joinpoint; National Cancer Institute, Bethesda, MD) to test for statistical significance in change over time.
WHAT IS THE HEALTH DISPARITIES CALCULATOR?
HD*Calc is statistical software that was created as an extension of the 2 National Cancer Institute monographs. It can be used with any population-based data. HD*Calc generates multiple indices to evaluate and monitor health disparities (http://seer.cancer.gov/hdcalc), enabling users to examine trends in disparity among multiple groups. The tool calculates results for 11 existing summary measures for any inequality factor included in a data set, such as race, ethnicity, income, education, or geographic region. As shown in Table 1, these existing measures vary in their characteristics. HD*Calc allows researchers to compare the 11 measures to select the set of measures that best capture the nuances of their data.
TABLE 1—
Summary Table of Advantages and Disadvantages of the Health Disparities Calculator Health Disparity Measures
| Disparity Measure | Absolute or Relative | Reference Group | All Social Groups | Reflect SES Gradient | Social Group Weighting | Inequality Aversion Parameter | Graphical Analog |
| Absolute difference | Absolute | Best | No | Yes | No | No | Yes |
| Relative difference | Relative | Best | No | Yes | No | No | Yes |
| Slope index of inequality | Absolute | Average | Yes | Yes | Yes | No | Yes |
| Relative index of inequality | Relative | Average | Yes | Yes | Yes | No | Yes |
| Index of disparity | Relative | Best | Yes | No | No | No | No |
| Relative concentration index | Relative | Average | Yes | Yes | Yes | Yes | Yes |
| Absolute concentration index | Absolute | Average | Yes | Yes | Yes | Yes | Yes |
| Between group variance | Absolute | Average | Yes | No | Yes | Yes | No |
| Theil index | Relative | Average | Yes | No | Yes | Yes | No |
| Mean log deviation | Relative | Average | Yes | No | Yes | Yes | No |
| Kunst—Mackenbach index | Relative | Best | Yes | Yes | Yes | Yes | Yes |
Note. SES = socioeconomic status.
HD*Calc has been used to explore cancer control outcomes including screening incidence, survival, and mortality,8–10 but HD*Calc is not limited to use with cancer data. A hyperlink to the tool is posted on numerous Web sites and social media platforms. The US Environmental Protection Agency and the King County Public Health Department in Seattle, Washington, are both using HD*Calc to examine and compare trends in disparities indices with their own data.11
HD*Calc has many cancer applications. For example, disparity trends in cervical cancer incidence by race and ethnicity are difficult to interpret without specifying whether absolute or relative disparities are more important. Cervical cancer incidence has been generally declining, but it has been declining faster among those with lower rates. In this case, relative disparities are increasing, but absolute disparities are decreasing. HD*Calc can be used to graphically present how these relative and absolute disparities vary. HD*Calc helps overcome barriers to computing and graphing inequality indices, as summarized in Table 2.
TABLE 2—
Barriers to Disparity Measurement and How the Health Disparities Calculator Helps Overcome Them
| Barrier | How HD*Calc Helps Overcome the Barrier |
| How can I compute inequality indices? | HD*Calc easily computes 11 indices on any data. |
| How can I compare inequality indices? | HD*Calc graphically displays results of 11 indices. |
| How do I interpret the different indices? | The case study monograph provides examples.7 |
| Should I measure absolute or relative disparity? | Both monographs6,7 address this and other questions. HD*Calc generates 4 absolute and 7 relative summary measures of disparity so you can visually compare the results of different absolute and relative measures. |
| How can I find out more about HD*Calc? | An HD*Calc Webinar and several HD*Calc Tutorials summarize the rationale behind the tool and help you get started. |
| What if I want something shorter than the Webinar and tutorials to begin with? | Download the fact sheet, Health Disparities Calculator (PDF). |
| How can I obtain HD*Calc? | It is freeware: Download HD*Calc version 1.2.3. |
| How do I get technical support in using HD*Calc? | Please send questions or comments to hdcalculator@imsweb.com. |
Note. HD*Calc = Health Disparities Calculator (http://seer.cancer.gov/hdcalc); PDF = portable document format.
CONCLUSIONS AND RECOMMENDATIONS
HD*Calc is a powerful tool for public health research, policy, planning, program development, and evaluation. It is being used for monitoring and planning in public health departments and federal agencies and is available for use in research and public health practice settings free of charge. HD*Calc is also a teaching tool for use in schools of public health, departments of health policy and health services research, and in training. Plans are under way to translate HD*Calc into Spanish and Portuguese. HD*Calc will advance the understanding of and ultimately support the Healthy People goal to eliminate health disparities. ■
Acknowledgments
The authors would like to acknowledge Sam Harper, Steve Scoppa, and Dave Campbell for development and support of HD*Calc software.
References
- 1.Sen A, Foster JE. On Economic Inequality. Oxford, UK: Clarendon Press; 1997. [Google Scholar]
- 2.Ravaillion M. Competing concepts of inequality in the globalization debate. In: Collins S, Graham C, editors. Brookings Trade Forum. Washington, DC: Brookings Institution; 2004. pp. 1–38. [Google Scholar]
- 3. Healthy People 2010. Available at: http://www.cdc.gov/nchs/healthy_people/hp2010.htm. Accessed May 5, 2014.
- 4. Healthy People 2020. Available at: http://healthypeople.gov/2020/about/DisparitiesAbout.aspx. Accessed May 5, 2014.
- 5.Pearcy JN, Keppel KG. A summary measure of health disparity. Public Health Rep. 2002;117(3):273–280. doi: 10.1016/S0033-3549(04)50161-9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Harper S, Lynch J. Bethesda, MD: National Cancer Institute; 2005. Methods for measuring cancer disparities: using data relevant to Healthy People 2010 cancer-related objectives. NCI Cancer Surveillance Monograph Series, Number 6. NIH Pub. No. 05–5777. [Google Scholar]
- 7.Harper S, Lynch J. Bethesda, MD: National Cancer Institute; 2007. Selected comparisons of measures of health disparities: a review using databases relevant to Healthy People 2010 cancer-related objectives. NCI Cancer Surveillance Monograph Series, Number 7. NIH Pub No. 07–6281. [Google Scholar]
- 8.Harper S, King NB, Meersman SC, Reichman ME, Breen N, Lynch J. Implicit value judgments in the measurement of health inequalities. Milbank Q. 2010;88(1):4–29. doi: 10.1111/j.1468-0009.2010.00587.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Harper S, Lynch J, Meersman SC, Breen N, Davis WW, Reichman MC. Trends in area–socioeconomic and race–ethnic disparities in breast cancer incidence, stage at diagnosis, screening, mortality, and survival among women ages 50 years and over (1987–2005) Cancer Epidemiol Biomarkers Prev. 2009;18(1):121–131. doi: 10.1158/1055-9965.EPI-08-0679. [DOI] [PubMed] [Google Scholar]
- 10.Harper S, Lynch J, Meersman SC, Breen N, Davis WW, Reichman ME. An overview of methods for monitoring social disparities in cancer with an example using trends in lung cancer incidence by area–socioeconomic position and race–ethnicity, 1992–2004. Am J Epidemiol. 2008;167(8):889–899. doi: 10.1093/aje/kwn016. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.National Cancer Institute. Research to reality. Measuring for improvement: the Health Disparities Calculator (HD*Calc). 2012. Available at: https://researchtoreality.cancer.gov/cyber-seminars/measuring-improvement-health-disparities-calculator-hdcalc. Accessed June 10, 2013.