Raven's Matrices are an excellent means of approximating G by measuring IQ. It uses pattern matching and manipulation, which is useful cross-culturally because it doesn't require literacy, understanding a specific language, or familiarity with specific cultural knowledge. E.g. a college entrance exam in the West might estimate your IQ by asking paragraph comprehension questions about a passage covering Julius Caesar crossing the Rubicon. This would be appropriate when comparing you to other Westerners, but it'd be useless for comparing you to people who're illiterate, dont speak English, and have never heard of the Rubicon River. Raven's Matrices works equally well for any demographic and is the gold standard for these types of international comparisons.