This model essentially represents an economy wherein every person spends exactly what they make, and in the real world, there are plenty of people who behave th

This model essentially represents an economy wherein every person spends exactly what they make, and in the real world, there are plenty of people who behave that way (at every position on the wealth spectrum). However, it also ignores the fact that for the most part, people are not forced to live that way. Sure, there's a certain minimum cost associated with simply staying alive, but there's also tremendous potential for people to save and/or invest (a portion of) their money rather than spend it, which in turn may increase their likelihood of being on the receiving end of other people's "random" expenses. It also ignores the fact that for every dollar spent in this economy, we can assume that a dollar of value is received in return. If a person spends a dollar truly randomly (or frivolously), then that expense has an opportunity cost, and in many cases (above a baseline for basic living expenses), that dollar would be better spent/invested in activities that will increase the person's future money-making power. I suppose if all those points were included in the model, we'd probably see even more inequality in the wealth distribution at the top end, but on the middle-to-low end, there's no reason it couldn't be much flatter; when people fall on hard times (as all will eventually), they can make the difficult-but-necessary decision to spend less than they make, thereby slowing or reversing any downward trend. Philanthropic activity would also help the unlucky few on the extreme lower edge of the distribution to bounce back quickly. Of course, the real problem in this scenario is that we should never underestimate the number of people who just don't care - or those who spend their money more "randomly" than not, with little concern for the future. Those are the same people who later on will be lining the streets protesting about how "unfair" the system is when they're finally broke.