About 8% of the world's population is considered 'white'. That number would be much lower if the Chinese had colonized the New World. The Chinese had the compass (for sailing), gunpowder (for fighting) and the printing press (for propaganda and administration) long before Europeans, but they lacked the motivation to colonize the New World. The Chinese weren't desperate for resources and they lacked the internal strife that incited Europe to explore and populate America. But, they're coming here now. Every ethnicity is trying to get here and white people just don't have enough kids with one another to maintain the 8% figure. In Europe, the dynamic is even more extreme where people of ME descent have tons of kids while young white people are abandoning the institution of marriage altogether.
What will preserve and expand the so-called white gene pool is gene selection technology. In the near future, parents are going to select recessive white genes over the alternative. They'll select blue and green eyes over brown, light skin over dark, straight fair hair over kinky, and so on.