How are country codes allocated globally?

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Country codes, which are the numerical prefixes you dial to reach a telephone subscriber in another country, are allocated globally by the International Telecommunication Union (ITU). Specifically, the ITU's Telecommunication Standardization Sector (ITU-T) is responsible for defining and maintaining the global numbering plan under ITU-T Recommendation E.164.

Here's how the allocation process works:

Establishing the Global Numbering Plan (E.164):
The ITU-T Recommendation E.164 lays out the foundational framework for international telephone numbers. This standard dictates that an international number can have a maximum of 15 digits and is composed of a Country Code (CC) and a National (Significant) Number (N(S)N). The N(S)N includes the National Destination Code (often an area code) and the Subscriber Number. This global blueprint ensures that every phone number worldwide is unique and that calls can be routed correctly across international networks.



Dividing the World into Numbering Zones:
Historically, in the early 1960s, the ITU's predecessor, the CCITT, divided the world into "numbering zones" based loosely on geographical regions and, to some extent, the telecommunications switzerland phone number list capacity and influence of countries at the time. These zones generally correspond to the first digit of the country code:

Zone 1: North America (Canada, USA, and many Caribbean nations share country code 1).
Zone 2: Primarily Africa, along with some Atlantic islands (codes typically start with 2).
Zones 3 & 4: Europe (codes typically start with 3 or 4).
Zone 5: South and Central America (codes typically start with 5).
Zone 6: Southeast Asia and Oceania (codes typically start with 6).
Zone 7: Russia and Kazakhstan (shared country code 7).
Zone 8: East Asia and special services (codes typically start with 8).
Zone 9: West, Central, and South Asia, and parts of Eastern Europe (codes typically start with 9).
Assignment of Country Codes:

Application by UN Member States: Any country or autonomous telephone administration (typically an ITU Member State) wishing to participate in the international public switched telephone network (PSTN) and have its own unique international dialing code must apply to the ITU.
ITU-T Study Group 2 (SG2): The ITU-T's Study Group 2 is the primary body responsible for developing the criteria and procedures for the reservation, assignment, and reclamation of E.164 country codes. They work to ensure the efficient and effective utilization of these global numbering resources.
Director of the Telecommunication Standardization Bureau (TSB): The Director of the TSB, the permanent secretariat of the ITU-T, is ultimately responsible for the formal assignment and reclamation of these E.164 country codes for geographic areas, global services, and international networks.
Criteria for Assignment: While the initial allocation was somewhat based on geographic zones and historical context, newer assignments and management adhere to principles outlined in ITU-T Recommendations like E.164.1 and E.190. These recommendations focus on efficient resource management, ensuring uniqueness, and accommodating new requirements, including those for global services (e.g., satellite systems like 870 or Universal International Freephone Numbers 800) and even potentially for Machine-to-Machine (M2M)/IoT devices in the future.
Factors Influencing Code Length:

Early Assignments: Historically, countries with larger telecommunications networks or those that were major players in the early days of international telecommunications often received shorter, single-digit or two-digit codes (e.g., 1 for North America, 33 for France, 44 for the UK). This was partly to minimize dialing time in an era of mechanical exchanges.
Subsequent Allocations: As more countries joined the global network and numbering resources became more constrained, longer three-digit country codes became more common.
In summary, country codes are not randomly assigned. They are systematically allocated by the ITU based on an internationally agreed-upon numbering plan (E.164), historical regional divisions, and a formal application process managed by the ITU-T to ensure global interoperability and efficient use of finite numbering resources.