For purposes of color-coding on this map, companies are divided into those that established their ESOPs before 1980, those that established their ESOPs between 1990 and 1999, and so on, as shown in the set of colored pointers and corresponding labels under the map. To limit the companies to those in one or more year groups, click/tap a colored pointer or its label (like "1990-1999"); to restore the original view of all companies, click/tap "Year Established Range" to the left of the pointers and labels. Alternatively, once you have selected one or more groups, you may click/tap the tag that appears for a group to remove it from your view.
A note about older dates: In 1974, ESOPs gained a statutory basis with the passage of ERISA (the Employee Retirement Income Security Act). Plans with start dates before that either are stock bonus plans that later filed as ESOPs or pre-statutory ESOPs that needed individual IRS approval (ESOP creator Louis Kelso designed the first such plan in 1956).
You can explore the map by zooming in and out or by using the search box at the upper right of the map. (Selecting a search result will limit the map to that company. To restore the original screen, you can, for example, click/tap the tag for your search results that appear near the bottom of the map area, or click/tap the small circular arrow in the upper left of the map.)
To group the map by other parameters, hover over or click/tap "Year Established Range" in the lower-left portion of the map and select a grouping from the menu that pops up.