American Tower is a holding company. Through its subsidiaries, the company is a real estate investment trusts and an independent owner, operator and developer of multitenant communications real estate. The company's primary business is the leasing of space on communications sites to wireless service providers, radio and television broadcast companies, wireless data providers, government agencies and municipalities and tenants in a number of other industries. The company also provides tower-related services, including site acquisition, zoning and permitting and structural analysis, which primarily support the company's site leasing business, including the addition of new tenants and equipment on its sites.

Crown Castle International is a holding company. Through its subsidiaries, the company owns, operates and leases shared communications infrastructure that is geographically dispersed throughout the U.S., including towers and other structures, such as rooftops (collectively, towers), and fiber primarily supporting small cell networks (small cells) and fiber solutions. The company's towers, fiber and small cells assets are collectively referred to herein as communications infrastructure. The company's core business is providing access, including space or capacity, to its shared communications infrastructure via long-term contracts in various forms, including lease, license, sublease and service agreements.

MSCI is a provider of decision support tools and services for the global investment community. The company's segments are: Index, in which Clients use the company's indexes in various areas of the investment process, including index-linked product creation; Analytics, which provides risk management, performance attribution and portfolio management content, applications and services; Environmental, Social and Governance (ESG), which helps institutional investors understand how ESG considerations can impact the long-term risk and reward of their portfolio and individual security-level investments; and Real Estate, which includes research, reporting, market data and benchmarking offerings.