i16_Census_Tract_EconomicallyDistressedAreas_2023

<p><span style='background-color:rgb(255,255,255); color:rgb(76,76,76); font-family:&quot;Segoe UI&quot;, Arial, sans-serif; font-size:13.3333px;'><span style='display:inline !important; float:none; font-style:normal; font-variant-caps:normal; font-variant-ligatures:normal; font-weight:400; letter-spacing:normal; text-align:left; text-decoration-color:initial; text-decoration-style:initial; text-indent:0px; text-transform:none; word-spacing:0px;'>The IRWM web based EDA mapping tool uses this GIS layer. Created by joining ACS 2019-2023 5 year estimates to the 2020 Census Tract feature class. The TIGER/Line Files are shapefiles and related database files (.dbf) that are an extract of selected geographic and cartographic information from the U.S. Census Bureau's Master Address File / Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER) Database (MTDB). The MTDB represents a seamless national file with no overlaps or gaps between parts, however, each TIGER/Line File is designed to stand alone as an independent data set, or they can be combined to cover the entire nation. Census tracts are small, relatively permanent statistical subdivisions of a county or equivalent entity, and were defined by local participants as part of the 2020 Census Participant Statistical Areas Program. The Census Bureau delineated the census tracts in situations where no local participant existed or where all the potential participants declined to participate. The primary purpose of census tracts is to provide a stable set of geographic units for the presentation of census data and comparison back to previous decennial censuses. Census tracts generally have a population size between 1,200 and 8,000 people, with an optimum size of 4,000 people. When first delineated, census tracts were designed to be homogeneous with respect to population characteristics, economic status, and living conditions. The spatial size of census tracts varies widely depending on the density of settlement. Physical changes in street patterns caused by highway construction, new development, and so forth, may require boundary revisions. In addition, census tracts occasionally are split due to population growth, or combined as a result of substantial population decline. Census tract boundaries generally follow visible and identifiable features. They may follow legal boundaries such as minor civil division (MCD) or incorporated place boundaries in some States and situations to allow for census tract-to-governmental unit relationships where the governmental boundaries tend to remain unchanged between censuses. State and county boundaries always are census tract boundaries in the standard census geographic hierarchy. In a few rare instances, a census tract may consist of noncontiguous areas. These noncontiguous areas may occur where the census tracts are coextensive with all or parts of legal entities that are themselves noncontiguous. For the 2020 Census, the census tract code range of 9400 through 9499 was enforced for census tracts that include a majority American Indian population according to Census 2020 data and/or their area was primarily covered by federally recognized American Indian reservations and/or off-reservation trust lands; the code range 9800 through 9899 was enforced for those census tracts that contained little or no population and represented a relatively large special land use area such as a National Park, military installation, or a business/industrial park; and the code range 9900 through 9998 was enforced for those census tracts that contained only water area, no land area.</span></span></p>

本数据集供基于网页的IRWM探索性数据分析（EDA, Exploratory Data Analysis）制图工具使用。该数据集通过将2019-2023年美国社区调查（ACS, American Community Survey）5年估算数据与2020年人口普查街区组（Census Tract）要素类关联构建而成。
TIGER/Line文件（TIGER/Line Files）为形状文件（shapefile）及相关数据库文件（.dbf），是从美国人口普查局主地址文件/拓扑集成地理编码与参考（MAF/TIGER）数据库（MTDB）中提取的精选地理与制图信息子集。MTDB为无缝全国数据集，各部分间无重叠与间隙，但单个TIGER/Line文件既可作为独立数据集单独使用，也可组合使用以覆盖全美全域。
人口普查街区组是县或等效行政单元内规模较小、相对稳定的统计分区，由本地参与者作为2020年人口普查参与者统计区域计划的一部分划定。若不存在本地参与者或所有潜在参与者均拒绝参与，则由美国人口普查局负责划定。普查街区组的核心用途是提供一套稳定的地理单元，用于展示人口普查数据并与历次十年一次的人口普查数据进行对比。
普查街区组的人口规模通常介于1200至8000人之间，最优规模为4000人。最初划定时，普查街区组旨在实现人口特征、经济状况与生活条件的同质性。其空间范围因定居密度差异而存在显著波动。公路建设、新开发项目等引发的街道格局物理变化，可能需要对街区组边界进行修订。此外，普查街区组有时会因人口增长而拆分，或因人口大幅减少而合并。
普查街区组的边界通常遵循可见且可识别的地物。在部分州及场景中，边界也可遵循小民政分区（MCD, Minor Civil Division）或已建制地方的法定边界，以建立普查街区组与政府单元的对应关系——这类政府边界在两次人口普查之间通常保持稳定。在标准普查地理层级体系中，州界与县界始终同时作为普查街区组的边界。
在极少数情形下，普查街区组可能包含非连片区域。这类非连片区域通常出现在普查街区组与本身为非连片的法定实体的全部或部分区域重合的场景中。
针对2020年人口普查，三类普查街区组使用了专属代码段：其一，依据2020年人口普查数据，人口以美国印第安人为主，或区域主要由联邦认可的美国印第安人保留地及/或保留地外信托土地覆盖的普查街区组，使用9400至9499的代码范围；其二，人口极少或无人口，且代表相对大型特殊土地利用区域（如国家公园、军事基地、商业/工业园区）的普查街区组，使用9800至9899的代码范围；其三，仅包含水域区域、无陆地区域的普查街区组，使用9900至9998的代码范围。