Do Oxfam's figures on wealth add up?

The richest 1% of the world's population now has as much wealth as the rest of the world combined, according to Oxfam.

It uses data from Credit Suisse from October for the report, which urges leaders meeting in Davos this week to take action on inequality.

Oxfam also calculated that the richest 62 people in the world had as much wealth as the poorest half of the global population.

But how do they calculate those figures?