Among those “too poor” to make the list is Japan's Yazaki family, worth an estimated $3.1 billion.

Yazaki Corporation is a global leader in the research, development, and delivery of vehicle power, data, and display for automotive applications. Yazaki produces wire harnesses, power distribution and control products, connectors, driver information displays, hybrid and electric vehicle products, and sensors.

Company established in Nakaizumi, Iwata-shi, Shizuoka, under the private ownership of Hiroyoshi Yazaki for the purpose of producing and selling plastic products.