all countries in the world at five year intervals (United Nations 2006).<sup>19</sup> The missing end decades are calculated for 116 countries for which data are lacking, most of them for the 1960s and 1970s.<sup>20</sup> Trends in International Migrant Stock database thus can be used to estimate growth rates by estimating missing totals in years for which censuses are not available, and it provides a consistent set of totals over time for countries for that have data of insufficient quality.

An important difference between the matrices presented in this article and the Trends in International Migrant Stock database is the treatment of refugees. While refugees are generally enumerated in developed country censuses, this is not always the case for developing countries. Refugees interned in camps are less likely to be surveyed at the time of census. Making allowances for these refugees, the Trends in International Migrant Stock database adds to the number of migrants refugees reported by the United Nations Refugee Agency and the United Nations Relief and Works Agency for developing countries that are not likely to have included the refuges in their census data. Since the majority of developed countries record refugees alongside other migrants on a bilateral basis, there are normally no remedial measures for removing them. Similarly, for developing countries for which no census data are available, it is impossible to know whether the numbers contained in Trends in International Migrant Stock database include refugees. For the cases that rely on the Trends in International Migrant Stock database, the number of refugees is subtracted from the totals, with the intention of removing refugees in camps from the total, since the focus is on economic migration.<sup>21</sup> COUNTRIES WITH VERY POOR DATA. For the 59 destination countries for which there are two or fewer census data points, it is impossible to meaningfully interpolate missing census totals or bilateral numbers. In these cases the census totals detailed in the Trends in International Migrant Stock are used. This has the advantage of ensuring consistent totals for the number of migrants in each of the five census periods. The average bilateral shares from the censuses with data are then applied to these totals to derive bilateral data for each census round.

Finally, there are six destination countries for which bilateral data are completely lacking.<sup>22</sup> In these cases, data for all the other countries in the subregion are used to 19 The 2008 revision includes data only for 1990–2010. To ensure consistent figures over time, the 2005 revision, which covers 1960–2005, was used instead.

20 Taiwan, China, and Norfolk Island pose an additional problem, since the United Nations does not provide data for these locations, so migrant totals in other years cannot be calculated. For these two areas, therefore, the numbers of migrants are set to zero in the earlier decades for which data are lacking.

21 In the case of Palestine, for which the UN totals consist entirely of refugees, these totals are not removed. It is possible to calculate migrant totals for Palestine in other decades.

22 The six countries are China, Eritrea, Maldives, Qatar, Somalia, and Democratic People‘s Republic of Korea. Of these, , Eritrea, and Somalia have been affected by conflict. China has conducted censuses over the period, but their definition of migration is not compatible with the definitions used throughout the article.

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