National Getis-Ord Gi* statistics for select populations; 1990-2019

Local Getis-Ord Gi* statistics were calculated as a measure of residential segregation. Measures were calculated at the census tract level based on the proportion of non-Hispanic White, non-Hispanic Black, non-Hispanic Asian [and Pacific Islander for 1990 and 2000 census], Hispanic, and immigrant persons (regardless of country of origin; 2008-2012 only) per census tract. Gi* statistics are Z-scores that compare the proportion of the population in the focal tract and its neighboring tracts to the average proportion of a larger geographic unit. For the majority of tracts, the larger geographic unit was the Core-Based Statistical Area (CBSA) these tracts belonged to. The county was used as the larger unit for tracts that fell outside the boundaries of a CBSA.<br><br>Data for the measures were obtained from the IPUMS National Historical Geographic Information System (NHGIS) data finder. Data were downloaded for the 1990 and 2000 census, and the 2006-2009, 2008-2012 (Immigrant segregation only), 2010-2014, and 2015-2019 5-year American Community Survey (ACS) estimates. Geographically standardized time series tables were used for 1990 and 2000 census data. All other ACS data were standardized to 2010 census tract boundaries.<br><br>G*statistics were calculated using both Rook and Queen conceptualization of spatial relationships. With Rook contiguity, neighbors are determined by those that share a common edge only, while Queen contiguity neighbors are those that share both an edge or a "corner" (common vertex). See detailed documentation for further details.<br>

局部Getis-Ord Gi*统计量被用作居住隔离程度的衡量指标。该指标以普查区（census tract）为计算单元，基于各普查区内非西班牙裔白人、非西班牙裔黑人、非西班牙裔亚裔[1990年和2000年普查还包含太平洋岛民]、西班牙裔以及移民人口（无论原籍国；仅2008-2012年数据有效）的占比进行测算。Gi*统计量属于Z分数，用于将目标普查区及其邻区的人口占比，与更大地理单元的平均人口占比进行对比。对于绝大多数普查区而言，该更大地理单元为其所属的核心基于统计区域（Core-Based Statistical Area, CBSA）；对于位于CBSA边界之外的普查区，则以县作为更大地理单元。

本数据集的指标数据源自IPUMS全国历史地理信息系统（IPUMS National Historical Geographic Information System, NHGIS）数据查询平台。我们获取了1990年、2000年全国人口普查数据，以及2006-2009、2008-2012（仅用于移民隔离测算）、2010-2014与2015-2019五年期美国社区调查（American Community Survey, ACS）估算数据。1990年和2000年的普查数据采用了地理标准化时序表格；其余所有ACS数据均被统一校准至2010年普查区边界标准。

Gi*统计量的测算同时采用了罗克邻接（Rook）与奎因邻接（Queen）两种空间关系概念化方式。其中罗克邻接仅将共享共同边界的区域判定为邻区，而奎因邻接则将共享边界或公共顶点（即共享角落）的区域均视为邻区。更多细节请参阅官方详细文档。