You don&#x27;t have to assume zero sum in general. Just that some interactions can be zero or negative sum. The simple example is monopoly rents: monopolists can increase their share of total profits without increasing value delivered.<p>By a lot of measures, the financial industry captures a lot more money than they did in previous decades. But it&#x27;s far from clear that they&#x27;re delivering a lot more value, and given that computers have drastically reduced their costs, it&#x27;s reasonable to expect them to be smaller, not larger. As a start, this has some good graphs:<p><a href="http:&#x2F;&#x2F;esoltas.blogspot.com&#x2F;2013&#x2F;02&#x2F;5-more-graphs-on-finance.html" rel="nofollow">http:&#x2F;&#x2F;esoltas.blogspot.com&#x2F;2013&#x2F;02&#x2F;5-more-graphs-on-finance...</a><p>And here are a couple more general-audience articles:<p><a href="http:&#x2F;&#x2F;blogs.reuters.com&#x2F;felix-salmon&#x2F;2011&#x2F;03&#x2F;30&#x2F;chart-of-the-day-us-financial-profits&#x2F;" rel="nofollow">http:&#x2F;&#x2F;blogs.reuters.com&#x2F;felix-salmon&#x2F;2011&#x2F;03&#x2F;30&#x2F;chart-of-th...</a><p><a href="http:&#x2F;&#x2F;blogs.wsj.com&#x2F;economics&#x2F;2011&#x2F;12&#x2F;10&#x2F;number-of-the-week-finances-share-of-economy-continues-to-grow&#x2F;" rel="nofollow">http:&#x2F;&#x2F;blogs.wsj.com&#x2F;economics&#x2F;2011&#x2F;12&#x2F;10&#x2F;number-of-the-week...</a>