Share your insights or perspective on the financial matter presented in the input.

Why is the highest quintile the only quintile whose wealth exceeds its income? 
I think you came up with a worthy Masters/PhD research project, it is a great question. This is in Australia so it is difficult for me to have complete perspective.  However, I can speak about the US of A. To your first point relatively few people inherit their wealth.  According to a brief web search about 38% of billionaires, and 20% of millionaires inherited their wealth.  The rest are self-made. Again, in the US, income mobility is very common.  Some act like high level earners are just born that way, but studies have shown that a great deal of income mobility exists.  I personally know people that have grown up without indoor plumbing, and extremely poor but now earn in the top 5% of wage earners.   Quid's points are valid.  For example a Starbucks, new I-Phone, and a brake job on your car are somewhat catastrophic if your income is 50K/year, hurts if your income is 100K, and an inconvenience if you make 250K/year.  These situations are normal and happen regularly.  The first person may have to take a pay day loan to pay for these items, the second credit card interest, the third probably has the money in the bank.  All of this exaggerates the effect of an "emergency" on one's net worth.    To me there is also a chicken-and-egg effect in wealth building and income.  How does one build wealth?  By investing wisely, planning ahead, budgeting, delaying gratification, finding opportunities, etc...  Now if you take those same skills to your workplace isn't it likely you will receive more responsibility, promotions and raises?  I believe so.  And this too exaggerates the effect on one's net worth.  If investing helps you to earn more, then you will have more to invest. To me one of the untold stories of this graph is not just investing, but first building a stable financial base.  Having a sufficient emergency fund, having enough and the right kind of insurance, keeping loans to a minimum.  Without doing those things first investments might need to be withdrawn, often at an inopportune time, for emergency purposes. Thanks for asking this!