Political Systems:
* Constitutional Republics: The most common political system, with variations (e.g., parliamentary vs. presidential). Examples: USA, Canada, UK, Australia, New Zealand, Ireland.
* Constitutional Monarchies: Where a monarch is the head of state but their powers are limited by a constitution. Examples: UK, Canada, Australia, New Zealand.
Economic Systems:
* Mixed Economies: This is the most common system where both private and public sectors play significant roles. Examples: USA, Canada, UK, Australia, New Zealand.
* Capitalist Economies: Emphasize free markets and private ownership. Examples: USA, UK, Australia, New Zealand.
Legal Systems:
* Common Law Systems: Based on precedent and judge-made law. Examples: USA, UK, Canada, Australia, New Zealand.
* Civil Law Systems: Based on codified laws and statutes. While not as common in English-speaking countries, Louisiana in the US has a mixed system with significant civil law influence.
Education Systems:
* Compulsory Education: Most countries have compulsory education up to a certain age.
* Public and Private Education Systems: Most countries have both public and private schools, with variations in funding and access.
* Higher Education Systems: Widely varying systems, from centralized (UK) to decentralized (USA).
Healthcare Systems:
* Universal Healthcare: A system that provides healthcare to all citizens, funded by taxes. Examples: Canada, UK, Australia, New Zealand.
* Private Healthcare: A system where healthcare is primarily paid for by individuals. Examples: USA.
Other Systems:
* Social Welfare Systems: Examples include unemployment benefits, retirement pensions, and social security.
* Transportation Systems: Vary widely with a mix of public and private transportation options.
* Energy Systems: Vary widely with a mix of fossil fuel and renewable energy sources.
To give you a more accurate answer, please provide more information about the type of systems you're interested in. For example, are you looking for:
* The most common political system?
* The most common type of legal system?
* The most common healthcare system?
Once I have more context, I can provide you with a more specific answer.