Global Estimated Net Migration Grids by Decade: 1970-2000

The Global Estimated Net Migration by Decade: 1970-2000 data set provides estimates of net migration over the three decades from 1970 to 2000. Because of the lack of globally consistent data on migration, indirect estimation methods were used. The authors relied on a combination of data on spatial population distribution for four time slices (1970, 1980, 1990, and 2000) and subnational rates of natural increase in order to derive estimates of net migration on a 30 arc-second (~1km) grid cell basis. Net migration was estimated by subtracting the population in time period 2 from the population in time period 1, and then subtracting the natural increase (births minus deaths). The residual was considered to be net migration (in-migrants minus out-migrants). The authors ran 13 geospatial net migration estimation models based on outputs from the same number of imputation runs for urban and rural rates of natural increase.This data set represents the average of those runs. These data are reliable at broad scales of analysis (e.g. ecosystems or regions), but are generally not reliable for local level analyses. The data were produced for the United Kingdom Foresight project on Migration and Global Environmental Change.

全球每十年估计净迁移数据集（1970-2000年）提供了从1970年至2000年三十年间的净迁移估计。鉴于全球范围内缺乏一致的迁移数据，研究者们采用了间接估计方法。作者们综合了四个时间切片（1970年、1980年、1990年和2000年）的空间人口分布数据以及地方层面的自然增长率，以在30弧秒（约1公里）的网格单元基础上推导出净迁移估计值。净迁移的估算方法为从时期1的人口中减去时期2的人口，再减去自然增长率（出生数减去死亡数）。所得余量被视为净迁移（迁入者减去迁出者）。作者们基于相同数量的自然增长率城市和农村估计运行，建立了13个基于地理空间的净迁移估算模型。该数据集代表了这些运行的平均值。这些数据在广泛的尺度分析（如生态系统或区域）中具有较高的可靠性，但对于局部层面的分析则普遍不可靠。这些数据是为英国前瞻性项目关于迁移和全球环境变化而生产的。