The Country Similarity Index attempts to quantify how similar countries are to each other relative to other countries. The index is a statistically-based way to measure this. 20% of the index is based on politics. 10% of a country’s politics score (2% of the overall Country Similarity Index score) is allocated for the various ways countries allow movement between each other. This includes openness of borders, naturalization of immigrants, and birthright citizenship. The following is an explanation on how they were considered:
Visa Policy
There are no borders and no passport checks between many countries in Europe. This is known as the Schengen Area. Several groups of countries in the Western Hemisphere have this arrangement as well, including the Andean Community, the Caribbean Community, and also Central America-4, which includes El Salvador, Guatemala, Honduras, and Nicaragua. In Africa, Kenya, Tanzania, Uganda, South Sudan, Rwanda, and Burundi have opened their borders to each other. All the countries in the Gulf Cooperation Council have this as well, except for Qatar, since Saudi Arabia closed its border to it due to a political disagreement. The next level of freedom of movement between countries is mutually allowing travel without a visa. This is a very common arrangement between similar countries. Sometimes countries ban citizens of a certain country traveling to their country. Israelis are banned from the most countries, since many Muslim nations refuse them. Libya is at the other end of the spectrum, since it has banned the citizens of six different countries from entering. All this information is subject to change based on rapidly evolving governmental policies.
Wikipedia is the main source of the data:
https://en.wikipedia.org/wiki/Open_border
https://en.wikipedia.org/wiki/Travel_visa
https://en.wikipedia.org/wiki/List_of_citizenships_refused_entry_to_foreign_states
Countries were compared based on the level of freedom of movement between them:
No passport required
No visa required
E-Visa or Visa on Arrival required
Visa required
Forbidden to enter
Naturalization Requirements
In some countries, it is much harder to become a citizen than others. Most allow naturalization after residing in the country for a number of years. Latin American countries tend to have very lenient naturalization requirements, since many only require 3 or even 2 years of residence. The countries in the Persian Gulf, including Bahrain, United Arab Emirates, Oman, Qatar, all have residency requirements of at least 20 years. China is another country where it is extremely difficult to be naturalized. Citizenship can also be bought in countries as various as Canada, Cambodia, and Moldova. There are often limits on dual citizenship as well, so you may need to give up your previous citizenship to be naturalized.
The CIA Factbook is the main source of the data:
https://www.indexmundi.com/factbook/fields/citizenship
Countries were categorized into the following groups:
Years of residency required: 0-5, 5-10, 10+
Dual Citizenship: Allowed, Not Allowed
Selling of Citizenship: Allowed, Not Allowed
Welcoming Score
Some countries allow far more nationalities to enter their country visa-free than others. In general, less developed nations have less strict visa requirements for entrance. Visas in advance are not required for most nationalities in many Sub-Saharan African countries. Many developing countries rely on tourism and foreign investment as a key part of their economy. By allowing visa-free or visa-on-arrival access, they attract more visitors who can spend money on hotels, restaurants, and local businesses. On the other end of the spectrum, two countries require the citizens of every country to have a visa in advance: North Korea and Afghanistan.
The Passport Index is the main source of the data:
https://www.passportindex.org/welcoming-country-rank-2019.php
Countries were categorized by the number of nationalities they allow to enter visa-free:
160-200, 120-160, 80-120, 40-80, 0-40
Birthright Citizenship
The vast majority of countries that have birthright citizenship (jus soli) are located in the Western Hemisphere. In some countries rights to citizenship are based on some combination of birthplace, time of residency, and whether the parents grew up in the country or not. Furthermore, many countries only allow citizenship based on the citizenship of the birth parents (jus sanguinis).
The Library of Congress is the main source of the data:
https://maint.loc.gov/law/help/birthright-citizenship/birthright-citizenship-map.pdf
Countries were categorized into the following groups by percentage of immigrants:
UNIVERSAL – by birthplace
EITHER – by children of residents OR children who grew up there OR by same race
PARTIAL – by children of permanent residents / by children who grow up there / by same race BOTH – by children of permanent residents who grew up there
NONE – by parents