# _Data and methods_

We have two sources of data that enable us to shed light on this issue. First, we can replicate the earlier analysis of the 1993 VLSS using the 1998 VLSS data. As in the earlier VLSS analysis, we include deaths over the preceding ten years in our analysis of the 1998 VLSS data.8 We rank households by equivalent household consumption in the analysis of the 1993 and 1998 VLSS data, and then sort the children born during the preceding ten years into quintiles. Our quintiles are therefore quintiles of live births. We then produce quintile-specific life tables for each year, and thereby obtain quintilespecific infant and under-five morality rates. Second, we can compare these two sets of VLSS results with the DHS-based results reported by Gwatkin and others (2000). These show infant and under-five mortality rates for different quintiles of "wealth," where the wealth measure is obtained by means of a principal components analysis on a variety of indicators of household living standards<sup>9</sup> along the lines proposed by Filmer and Pritchett (1999). A point to bear in mind is that the quintiles in Gwatkin and others are quintiles of _households,_ not of live births. This makes comparison of the VLSS and DHS results somewhat awkward, since the lower wealth groups have higher fertility rates and hence have a share of live births that is in excess of their population share. This problem can be overcome, however, using concentration curves (Wagstaff, Paci, and van Doorslaer 1991; Kakwani, Wagstaff, and van Doorslaer 1997). In this case, these are formed by ranking live births by the living standards of the child's household, and then plotting on the horizontal axis the cumulative percent of live births so ranked and on the vertical axis the cumulative percent of deaths (infant or under-five). If deaths are concentrated among poorer households, the resultant curve-the _concentration_ curve-will lie above the diagonal, or _line of equality._ The further above the line of equality it lies, the greater the degree of concentration of deaths among poorer households.

## _Results on trends in socioeconomic inequalities_

Figure 4 shows for each of the three surveys the under-five mortality rates for each quintile of living standards. Over the period 1983-92, there was very little difference between the survival prospects of poor and better-off children in Vietnam. By

> **8** As elsewhere in the paper, we weight the 1998 data using the sample weights.

> 9 In the case of Vietnam, the list includes the following (mostly binary) indicators: has electricity; has radio; has television; has refrigerator; has bicycle; has motorcycle; has car; has telephone; has sewing machine; has a boat; has a plowing machine; has a motor scooter; number of members per sleeping room; if piped drinking water in residence; if piped drinking water in public tap; if inside well drinking water; if uses river, canal or surface water for drinking; if uses shared flush toilet; if has traditional pit latrine; if uses VIP latrine; if uses bush or field as latrine; if has a finished floor; if has concrete roofing; if has a roof of galvanized iron/aluminum; if has earth or sand floor; if has rough wood or bamboo flooring; if has natural material roofing; if rain for drinking water; if uses a public well; if has own flush toilet; if uses water from a tanker truck; if uses bottled water; if roof made of asbestos or iron sheeting; if floor is made of other materials.

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