'प्रतिकर्ष' (Push) और 'अपकर्ष' (Pull) कारक मुख्य रूप से निम्नलिखित में से किस जनसांख्यिकीय घटक से संबंधित हैं?

In traditional anthropological classification of human races, which racial group was characterized as 'yellow-skinned'?

What is the approximate estimated proportion of ecumene (habitable) and non-ecumene (uninhabitable/sparsely inhabited) areas on the Earth's surface?