This article(https://www.counterpunch.org/2018/08/07/trillion-dollar-companies-the-apple-empire-and-concentrated-markets/)

suggests, based on significant evidence, that competition in US markets is not only constrained, but is becoming less so, asfewer companies dominate business(https://www.brookings.edu/research/the-state-of-competition-and-dynamism-facts-about-concentration-start-ups-and-related-policies/)

The high profits and rising stock markets we have seen recently are significantly linked to this, rather than to a more competitive economy.

Our model of Supply & Demand is based on a model of perfectly competitive markets. If our markets are not competitive, how does that affect this model?

Read the first article and the full Introduction (at least) to the Brookings study.

Submit your answer in the box. It should be a few paragraphs long and include a reference to an additional academic-level outside evidence to back up what you are saying.