SOCIAL INEQUALITY AND HEALTH IN MÉXICO 1990-1997: INDIVIDUAL AND POLICY PATHWAYS 1
Social Inequality and Health in México 1990-1997: Individual and Policy
Pathways - "Former: Impact of Income Inequalities on Mexico's
Popoulation Health"
Adolfo Martínez Valle, The Johns Hopkins University
7 de Diciembre de 2001
ABSTRACT
AIMS: To study how social inequality has influenced the health status of the Mexican population at the individual level from a social class perspective as well as the state level from a policy perspective between 1990 and 1996. Explore the individual and policy pathways through which social inequality affects health.
METHODS: To empirically examine the social class gradient in perceived health in Mexico a secondary cross-sectional analysis was designed using logistic multiple regression models. To empirically examine the association between social inequality and health across states, pooled cross-sectional data was used. Secondary analysis was conducted for the 32 Mexican states for 1990 and 1996 using general estimation equation (GEE) models. Path analysis was performed to explore how the electoral strength of opposition political parties shape health care resource allocation decisions which in turn influence population health.
RESULTS: The cross-sectional individual-level analysis provided empirical evidence that the lower the social class, the poorer the perception of health. The results of the pooled cross-sectional analysis indicated that social inequality across states was as expected, positively and significantly associated with maternal and infant mortality rates. The path analysis findings suggest that the electoral strength of PRD affects maternal mortality through its impact on the distribution of primary care physicians per capita via targeted health care expenditures.
CONCLUSIONS: Overall, the findings of this study provided empirical evidence that social inequality negatively influences health both at the individual and state level. The results also suggest that social inequality may be influencing health through both material and psychosocial mechanisms at the individual level and through policy mechanisms at the state level.
KEY WORDS: social inequality, socioeconomic determinants of health, social class, policy process, politics, Mexico.
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TABLE OF CONTENTS
1 INTRODUCTION
6 PART I: INDIVIDUAL EFFECTS OF SOCIAL INEQUALITY
METHODOLOGY 7 RESULTS 13 DISCUSSION 19
23 PART II: POLICY EFFECTS OF SOCIAL INEQUALITY
METHODOLOGY 24 RESULTS 27 PATH ANALYSIS 32 DISCUSSION 37
39 GENERAL CONCLUSIONS
43 REFERENCES
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INTRODUCTION
One of the most intriguing findings in the recent public health literature is the strong influence income inequality seems to have on health. The greater the income differences within populations, the worse their health differentials. This evidence suggests that worsening health conditions are associated with widening income disparities both across countries (Rodgers, 1979; Flegg, 1982; Waldmann, 1992; Wilkinson, 1992; Wennemo, 1993; Duleep, 1995; McIssac and Wilkinson, 1997; Judge et al, 1998; Armada, 2000) and within countries (Bronfman, 1992; Wilkinson, 1992 &1996; Lynch et al, 1998; Hollstein et al, 1998; Szwarchwald CL et al, 1999; Kawachi et al, 1999, 1997; Kennedy et al, 1998, 1996; Soobader and Leclere, 1999; Shi et al, 1999).
Examining the associations between socioeconomic inequalities and health differentials is not new. Research from the Anglo-Saxon tradition (Marmot and Wilkinson, 1999; Berkman and Kawachi, 2000) as well as from the Latin American school of social epidemiology (Almeida-Filho, 1999) has made extensive and important contributions in the past. The Anglo-Saxon tradition has provided empirical evidence of how socioeconomic status measured by social class, occupation, education, and income positively influences health across the social spectrum (Marmot and Wilkinson, 1999; Berkman and Kawachi, 2000). However, this research tradition has focused almost exclusively on individual social risk factors. This dissertation proposes to go beyond this individualistic approach by focusing on the social structure of inequality as an influencing factor on health. From this perspective, the underlying assumption is that health differentials across the social spectrum are closely related to the structure of a society, which in turn is shaped by social, economic and political processes.
This approach is similar in a way to the Latin American school of social epidemiology, which has emphasized the importance of class and the context under which social inequalities and its health consequences are manifested. However, Latin American research has mostly followed a theoretical approach and has not been able to provide strong empirical evidence of their important theoretical and conceptual contributions except for a few exceptions (Bronfman, 1992; Lozano et al, 2001). This dissertation sought to reduce this empirical gap in the Latin American literature.
The more recent income inequality approach has sparked a renewed interest in this field of inquiry with its revealing empirical findings. Despite its theoretical limitations it has drawn the attention of many FINAL PAHO REPORT ADOLFO MARTINEZ VALLE
SOCIAL INEQUALITY AND HEALTH IN MÉXICO 1990-1997: INDIVIDUAL AND POLICY PATHWAYS 4
public health researchers. There are three main reasons for this. First, income inequality has grown considerably both within and across most countries. Second, health differentials persist, despite overall health improvements in terms of life expectancy and other population health indicators. Third, social inequality including income can be a target for public policies seeking to improve both health and living conditions.
Most of these income inequality studies have been conducted in industrialized countries, mainly in Great Britain and the United States. Furthermore, many have failed to explicitly define a theoretical framework to guide their empirical approach. Therefore, the novelty of this dissertation lies in exploring if a similar association exists in Mexico, a middle-income country that has experienced both greater income disparities and population health inequalities over the past two decades. Studies have shown that income inequalities have worsened since the 1980s and continued through the 1990s, though at a lesser growth rate (Cortés, 1998; De la Torre, 1995; Lustig, 1998). Household survey data indicate that between 1984 and 1989 the income share of the bottom 90 percent of the total population decreased, while only the share of the top 10
ipercent increased (De la Torre, 1995). Using the Gini coefficient, income inequalities decreased from 0.53 in
ii1977 to 0.466 in 1984, increased from 0.504 in 1989 to 0.528 in 1994, decreased to 0.488 in 1996, and increased again to 0.509 in 1998 (INEGI, 1996; 1998; 2000). Overall, the degree of income inequality has increased by nearly 10 percent between 1984 and 1994. However, income is just one indicator of social
iiiinequality. The marginality index, an area-based indicator of relative deprivation also shows that social inequality has not improved substantially in Mexico. According to this index, marginality has been reduced in 17 out of the 32 Mexican states between 1990 and 1995, while the remaining 15 states have experienced higher marginality figures (CONAPO, 1998). This indicator was designed by the Mexican government to assess the degree of access to basic public services and infrastructure across both states and counties.
In Mexico population health has improved in the past two decades in terms of reducing mortality rates and increasing life expectancy. However, these average nationwide improvements hide the worsening of health conditions in at least two ways. First, they do not show the regional disparities within Mexico. The reductions in infant mortality across states were not the same between 1985 and 1995. The state with the highest reduction was Tlaxcala, where infant mortality was reduced from 38.2 to 30.4 children deaths less than 1 year of age per thousand live births. This 20 percent reduction contrasts with 5 percent reduction in Baja California, the lowest, which was reduced from 26.5 to 25.1 children deaths less than 1 year of age per FINAL PAHO REPORT ADOLFO MARTINEZ VALLE
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thousand live births. The poorest states (Guerrero, Chiapas, and Oaxaca) reduced their infant mortality rates 14 percent on average between 1985 and 1995, but still experienced the highest mortality rates (ranging from 48.4 in Chiapas to 44.6 in Guerrero in 1995) in Mexico among its 32 states (FUNSALUD, 1998). Furthermore, a previous study (Lozano, 1997) showed that child mortality in 1994 was almost two times higher in the poorer states, 523 per thousand children under 5 years of age (Guerrero, Chiapas, and Oaxaca) than in the richest ones, 278 per thousand (Distrito Federal, Nuevo Leon, Tamaulipas, Coahuila and Baja California Sur). Health inequalities are also manifested in the adult population. The poorer states have a mortality rate of 139 deaths per thousand adults between 15-59 years of age, while the richest states have a rate of 105 per thousand (Lozano, 1997).
Second, some indicators reveal deterioration in the health of the population. For example, infant and preschool mortality caused by nutritional deficiencies increased since 1982 after years of steady decline. This specific cause of mortality accounted for 1.5 percent of total infant mortality and 2.4 percent of total preschool mortality in 1982, increasing its percentages to 5.2 and 9.1 respectively in 1988 (Lustig, 1998). A more recent study shows that malnutrition inequalities have not been reduced significantly in the past decade
iv(Roldán JA et al, 2000). Poor states like Oaxaca and Chiapas show a malnutrition index of 35 in 2000, while
the richest states such as Nuevo Leon, Baja California and Distrito Federal present figures below 8 (Roldán JA et al, 2000). Thus, there is evidence that inequality may have an impact on health in the Mexican context. Furthermore, there is no consensus on why social inequality may affect health even if an empirical association is found. The main aim of this dissertation, therefore, was to study how social inequality has influenced the health status of the Mexican population at the individual and the state level between 1990 and 1996.
To achieve this goal this dissertation was organized as follows. To empirically examine the association between social inequality and health in the Mexican context this dissertation was divided in two parts. The first part analyzed how social inequality negatively influences health at the individual level. Using data from the Second National Health Survey (ENSA II, 1994) this level of cross-sectional analysis aims to investigate the degree and factors associated with the social class gradient in health status. Furthermore, it sought to explore the material and psychosocial pathways through which income inequality may affect health. The second part of this dissertation analyzes the association between social inequality and population health at the state level using several data sources including electoral data. This state level of analysis aimed to explore FINAL PAHO REPORT ADOLFO MARTINEZ VALLE
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the ecological and political pathways through which social inequality may influence health in Mexico. Finally, this study sought to draw some conclusions from its empirical findings including the policy implications of targeting social inequality to improve the health of the Mexican population.
PART I
INDIVIDUAL EFFECTS OF SOCIAL INEQUALITY
The purpose of this first part of the study is to examine the association between social inequality and individual health using both individual measures and an area-based indicator of relative deprivation. This level of analysis also seeks to explore the material and psychosocial mechanisms that associate mortality and morbidity gradients with social class differentials. To study the social class gradients in morbidity, the sample
vwas restricted to the occupied population aged 12 years and older. This sample was divided in two groups:
the urban working force and the rural working force. The first are those who worked in urban settings, while the rural were made up of people in agricultural related activities including the forestry and livestock industries. The final sample size was 13,062 individuals working in the urban sector and 4,614 working in the agricultural sector. The distinction was made because previous studies (INEGI, 1990; 1997; Bronfman, 1992; Bronfman et al, 1990; Bartra, 1991) have shown that urban and rural populations experience different
visocioeconomic living conditions. For example, approximately 93 percent of the urban population in Mexico
had access to drinking water services, while only 57 percent of the rural population had access to that kind of services (INEGI, 1997). A cross-sectional secondary analysis of the Second Mexican National Health Survey (ENSA II) will be conducted using logistic multivariate statistical models.
METHODOLOGY
Individual measures were developed from ENSA II conducted in 1994. ENSA II is a personal interview type of survey, using a stratified multistage probability sample of households. The primary sampling unit was a dwelling. For sampling purposes, the country was divided in five regions and a sample size of approximately 2,523 dwellings was drawn from each region. Table 1 presents how these regions are defined.
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Table 1
ENSA II regions
Region States Dwellings Individuals
(n) (n)
NORTH Baja California, Baja California Sur, Sonora, 2,570 4,905
Chihuahua, Sinaloa, Coahuila, Nuevo León,
Tamaulipas, Durango, Zacatecas
DF Mexico City Metropolitan Zone 2,520 5,139
CENTER San Luis Potosí, Guanajuato, Querétaro, 2,620 5,225
Michoacán, México, Tlaxcala, Nayarit,
Aguascalientes, Jalisco, Colima
SOUTH Morelos, Puebla, Veracruz, Campeche, Tabasco, 2,520 5,227
Yucatán, QROO
PASSPA Hidalgo, Oaxaca, Guerrero, Chiapas 2,520 4,887
PASSPA: Health Services Aid Program for the Uninsured Population
Within each region, the sample was proportionally distributed according to the population size of each of the 32 Mexican states, setting a minimum of 100 dwellings for the smallest states (Secretaría de Salud, 1994). ENSA II is representative of the Mexican population at both the national and the regional level. It contains information on health status and health care utilization of individuals, as well as demographic and socioeconomic characteristics of households and individuals. The survey has two questionnaires. The household questionnaire was designed to collect information for every household member, while the individual one collected information for every user of health services. The overall response rate was approximately 96.7 percent for both the household and the individual questionnaire. Data were obtained for 12,615 households, including 61,524 individuals (Secretaría de Salud, 1994).
The marginality index, an aggregated measure, was obtained from the National Population Council (CONAPO, 1998). This index was developed to measure the degree of marginality in each Mexican state and county. The index is an indicator of deprivation based on housing, income, and schooling information collected from the 1990 Mexican Census and the 1995 Population and Housing Count (CONAPO, 1998). ENSA II is linked to the state level marginality data by assigning a level of marginality to the state of residence of each individual. ENSA II is not designed to support state level estimation, however. To FINAL PAHO REPORT ADOLFO MARTINEZ VALLE
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determine whether each state is represented in ENSA II in proportion to its actual share of the Mexican population, the distribution of ENSA II was compared to the 1990 census and 1995 mid-count data. The ENSA II sample distribution is similar to the census data except for the PASSPA states, which were oversampled. The final data set for this analysis is composed of individual level data, but it also includes a contextual level measure, the marginality index at the state level.
HEALTH OUTCOMES
Two indicators of perceived health status are used as health outcomes in this study: self-assessed health and reported morbidity. Both the social class gradient literature and the income inequality approach have shown that these morbidity indicators are sensitive health indicators to the effects of social inequality (Marmot et al, 1991; Farmer and Ferraro, 1997; Kawachi et al, 1999a).
Self-assessed health is a measure that has been shown to have a strong predictive validity (Farmer and Ferraro; Idler and Benyamini, 1997). This indicator measures the perception that each individual surveyed had of its overall health status. This measure was originally rated on a 5-point scale: very poor, poor, average, good and very good. For the purposes of this study, it was transformed to a dichotomous measure equal to 1 if the response was average, poor or very poor.
Reported morbidity, on the other hand, is a health indicator that measures specific health problems such as heart disease, diabetes, digestive and respiratory diseases. This indicator captured health problems reported in the past two weeks, including illnesses, discomforts or accidents. The main health problems reported where respiratory diseases, muscle and bone related problems, gastrointestinal diseases, headaches, hypertension, mouth diseases, fever, diabetes, and cough. These health problems accounted for almost seventy percent of the total health problems reported in the ENSA II survey. This health outcome was also measured as dichotomous variable equal to 1 if the respondent suffered any health problem and 0 otherwise.
SOCIAL CLASS
To measure social inequalities, two approaches have been followed in the public health literature (Krieger et al, 1997; Muntaner et al, 2000). Social stratification, the first approach, is a hierarchical ordering of individuals according to the degree of education, type of occupation and income level (Krieger et al, 1997). Most studies use more than one dimension of stratification to better capture the effects of social inequalities on health. The class perspective, on the other hand, classifies individuals according to ownership of the means FINAL PAHO REPORT ADOLFO MARTINEZ VALLE
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of production, authority over others in the workplace, skills exercised in the job, and control over different types of assets (Wright, 1997). This study follows the first approach but it also incorporates elements of the class perspective such as business and land ownership.
ENSA II does not include all of these criteria of social class membership. For example, it only includes information on land ownership, but not on the size of the land. The operationalization of social class was therefore constructed following a stratification approach according to the occupation and education indicators available from ENSA II. This class operationalization was chosen to better measure its social gradient effects on health. Individuals were first stratified according to two broad occupation categories: the urban sector which comprised the manufacturing and the services industry and the rural sector which included all agricultural related economic activities. The urban labor force consisted of six occupational categories: employer, independent professional, employed, non-salaried workers and salaried workers. These occupational categories identified some of the technical aspects of work associated with prestige, wealth, skills and specific working conditions. The first two theoretically correspond to high-income socioeconomic status from a social stratification perspective and to a high social class or bourgeoisie from a standard class perspective. Education, measured by years of schooling, was also added as a criterion to avoid misclassification. This category therefore only included individuals whose occupation was either an independent professional or an employee of the manufacturing or services sector, which had at least a college
viidegree in addition to the employers, which had 9 or more years of schooling. The employed and non-
salaried categories were more difficult to classify because they did not indicate a specific social class position. Education was therefore added as an additional criterion to sort individuals into the corresponding social classes to account for their respective urban labor force skills. Several measures of socioeconomic status have been used simultaneously in many studies because using a single measure has not adequately captured the health effects of social inequality (Muntaner and Eaton, 2000; Berkman and Kawachi, 2000). Thus, the employed, which had 15 or more years of schooling, were classified in the high-class category, while the employed and non-salaried workers with 9 to 14 years of schooling were classified in the middle-high class. The non-salaried and salaried workers categories were sorted out into middle-low and low-income working class by years of schooling as well. The middle-low class were those that had between 7-8 years of schooling and the low-income working class corresponded to those that had 6 years or less of schooling. The education FINAL PAHO REPORT ADOLFO MARTINEZ VALLE
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dimension of social class was based on the Mexican occupational stratification estimated by the Economic Commission for Latin America and the Caribbean (CEPAL, 1997). The CEPAL stratifies occupations in three categories. The high category includes employers who have on average 9 years of schooling, managers with 13 years, and professionals with 15. The middle strata includes technicians who have 13 years of schooling, employees with 11 years, and merchants with 8. The low occupational category includes industrial and service workers who have on average between 6 and 7 years of schooling, and the agricultural workers who have 4 years of schooling on average. Table 1 shows the four categories of social class defined for the urban labor force according to the criteria described above.
Table 2
Urban social class operationalization
Variable Occupation Education
High Employer
Independent professional 15 or more years
Employed 15 or more years
Middle high Employed 9-14 years
Non-salaried worker 9-14 years
Salaried worker 9-14 years
Middle low Employed 7-8 years
Non-salaried worker 7-8 years
Salaried worker 7-8 years
Low Non-salaried worker 6 or less years
Salaried worker 6 or less years
The agricultural labor force consisted of five occupational categories: landowners including
viiiejidatarios, land tenants, self-employed, salaried workers and non-remunerated workers. Relations and size of land ownership generally determine the classification of social class in the rural areas. However, ENSA II did not provide any information on this regard. Education was again employed here to stratify the respective social classes. Additionally, a proxy for income was included as an additional criterion for agriculture class differentiation to reflect more accurately the material living conditions of the rural classes. This proxy for income was based on the number of durable goods each individual possessed: automobile, television, video cassette player, refrigerator, gas stove, and water heater. Four dichotomous variables were constructed: one, if FINAL PAHO REPORT ADOLFO MARTINEZ VALLE