Using 1999-2001 Luxembourg Income Study data, we examine cross-national patterns of age-specific poverty rates. Relative to 12 Western countries, Taiwan has a moderate child poverty rate but a much higher elderly poverty rate, leading to the largest elder-child poverty gap. We show that Taiwan significantly differs from the other countries in three factors - social welfare efficiency, market income inequality, and household composition - and document poverty differences across household type. Relative to other countries, Taiwan has a low rate of single-parent headed households, a high rate of older adults who live with family members, and fairly inefficient social welfare. Standardization and decomposition analyses systematically test effects of these factors across countries. Results indicate that Taiwan's low welfare efficiency makes the largest contribution to both child and elder poverty rates, but has a much more negative effect on elderly poverty. Older adults' higher rates of co-residence with family members has a strong ameliorating impact on elderly poverty. Implications in light of recent demographic and economic trends in Taiwan and similar East Asian countries are discussed.