Estimating private wealth is really a stab in the dark. The Credit Suisse Report you alluded to is highly inaccurate. Here's a quote from the article: "An obvious possibility is that Credit Suisse is just wrong. Compiling global wealth numbers is a considerable task. "

I deal with private off shore trusts, historical funds, etc. You will never get accurate figures from those two sectors due to its wall of secrecy.  For example, there is one private Sino financial firm whose assets is north of 10T. The public will never know this entity since it is totally private.

Here's an example of a more prosaic easily verifiable party: Jerry Picower. His last estimated public net worth according to Forbes was 1B. Mr. Picower passed away during the Bernie Madoff debacle. His estate settled with the Bankruptcy Trustee for 7.2 B for fraud. It was disclosed that his estate was north of 10B at the time of his demise. People on Wall St were stunned at the hidden wealth he amassed discreetly over time.