Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50 Page 51 Page 52 Page 53 Page 54 Page 55 Page 56 Page 57 Page 58 Page 59 Page 60 Page 61 Page 62 Page 63 Page 64 Page 65 Page 66 Page 67 Page 68 Page 69 Page 70 Page 71 Page 72 Page 73 Page 74 Page 75 Page 76 Page 77 Page 78 Page 79 Page 80 Page 81 Page 82 Page 83 Page 84 Page 85 Page 86 Page 87 Page 88 Page 89 Page 90 Page 91 Page 92 Page 93 Page 94 Page 95 Page 96 Page 97 Page 98 Page 99 Page 100 Page 101 Page 102 Page 103 Page 104 Page 105 Page 106 Page 107 Page 108AGING IN THE 21S T CENTURY 14 Longitudinal Cohort Design The HRS sample has been built up over time. Figure A-4 depicts the longitudinal cohort sample design. The initial 1992 HRS cohort consisted of persons born 1931 to 1941, who were then aged 51 to 61. Members of this first HRS cohort, now in their 70s and 80s, have been interviewed every two years since 1992. A second study was added in 1993, the Asset and Health Dynamics Among the Oldest Old, or AHEAD, which captured those born before 1924, who were 70 and older at the time. Then in 1998, the HRS and AHEAD cohorts were merged, and two new cohorts were enrolled to bridge the study age gaps for Americans over age 50. These birth cohorts are the Children of the Depression Era, or CODA, for those born 1924 to 1930, and the War Babies, for those born 1942 to 1947. Without refreshment, the HRS sample would age quickly and become irrelevant to pre-retire- ment ages. So HRS now employs a steady state design, replenishing the sample every six years with younger cohorts. In 2004, the HRS added the Early Baby Boomers (EBB), born 1948 to 1953, and in 2010 added the Mid Baby Boomers (MBB), born 1954 to 1959. The Late Baby Boomers (LBB), born 1960 to 1965, were added in 2016. For all cohorts, both members of a couple are included in the sample. To constrain costs, study recruitment was reduced in the steady state by nearly half from the levels of the original HRS cohort. This meant that lower numbers of minority households in the more recent cohorts became a concern. The HRS is an important resource for understanding caus- es of racial disparities in wealth and health, so maintaining the sample of minority participants is a priority. To address this need, a new initiative launched in the 2010 wave of data collection greatly expanded the minority sample in the EBB and MBB cohorts. Going Global The success of the HRS idea — a publicly avail- able, multidisciplinary, longitudinal study of the older population — has led to the proliferation of sister studies. The HRS is now the model for a growing network of harmonized longitudinal aging studies around the world — including England, Ireland, 20 European Union countries, Israel, Mexico, China, Japan, South Korea, India, Brazil, Northern Ireland, Scotland, and South Africa. The global network greatly enhances the value of each of its members, including the HRS itself, through sharing of ideas and methods. The international studies have attracted researchers from a variety of disciplines and all parts of the globe. The availability of comparably measured data in other countries with different policy structures, social environments, and histories provides opportunities for comparative research to shed light on causal relationships that even longitudinal analysis in a single country cannot accomplish. The growth of these studies expands the network of researchers using the HRS data and contributing innovative measurement ideas. FIGURE A-5  HRS scientific productivity 0 1500 2000 2500 3000 1995 2000 2005 2010 2015 500 1000 Reports Dissertations Books/book chapters Journal articles