I think the biggest problem of the 21st century is how to deal with minorities.

I think the environmental problem will be the number one item on the agenda of the 21st century... This is a problem that cannot be postponed.

The 21st century simply means open century.

I think Facebook's biggest problem is the glut of information that Facebook's power users are overwhelmed with.

The great challenge of the twenty-first century is to raise people everywhere to a decent standard of living while preserving as much of the rest of life as possible.

I think the biggest problem in clinical trials is that they are underpowered. And that fundamentally, the studies are just too small.