Buyers and Sellers create orders at various prices and lock them in, but the order is initially hidden from everyone. After the order has existed in the system for 2x interval it is published. Attempting to cancel an order has a 1 interval delay. Every interval, if buy and sell orders overlap, match up trades. Resolve the imbalance between buyers and sellers by picking the winning trades randomly. Add a bias to the randomisation process to prefer smaller quantity orders.
Since there's a delay between publishing and finalising trades, a stock with a high volume of trades is likely to have overlapping buy and sell orders almost all the time.
Want to understand the dynamics of the economy? Track the level, velocity and acceleration of debt.
This might surprise you, but mainstream economists completely ignore the role of banks in issuing credit and the impact that credit has on the economy.
Now, I'm all for including the banking sector in stories where it's relevant; but why is it so crucial to a story about debt and leverage?
But there is an enormous correlation between debt growth and employment, margin lending and stock prices, mortgage debt and house prices. Changes in debt levels and asset prices create a feedback loop where each causes the other to change. Debt induces a euphoric blindness to it's potential downsides.
If you look at the historical trend in the level of debt compared to income, there was a big build up of debt leading up to the 1929 crash and ensuing depression. Plus the ratio of debt to income got even worse during the depression as income levels fell.
Leading up to the 2008 collapse of Lehman Bros. & AIG, we had far more debt than the 1920's. More debt than the highest peak during the 30's depression.
Most of that debt is not going to be repaid, it's simply impossible. So the only question that remains is, how we are going to manage not paying these debts. Are we going to continue waiting until everyone has gone bankrupt? Depressing the economy until debts are back to reasonable levels, while the population becomes increasingly desperate for a solution. Or inflate our way out by giving everyone free money to pay their debts with? Levelling the wealth distribution a little, which will of course annoy those who have been responsibly saving for the future.
Both solutions have morality questions, both solutions cause a massive disruption to the economy and fabric of society.
The recorded history of the domestic dog demonstrates an explosion of variations in a relatively short time frame, driven by both natural and artificial selection criteria. Selective breeding can result in quite rapid and drastic changes to the form of an organism. Almost as if this rapid adaptation was a deliberately designed feature of life. There's no need for a hypothetical Noah to have carried more than one pair of dogs / wolves and still account for all of the variations we see today. Similarly, other kinds of animals, living in different ecosystems, with different selection pressure could exhibit the same rapid variations without requiring aeons of time elapsing.
On the other hand, in a stable environment, natural selection pressure can also serve to keep the form of organisms constant. eg Predators eating the weak, females choosing the mates that match their ideal image of the species. If you assume there was a period of massive disruption, where each organism must adapt to the new ecosystem they find themselves in, change can be very rapid.
Another point from the creationist / young earth / Intelligent Design side, ignoring any argument based on the story of creation or Adam. The young earth creationist who takes the story of Noah literally, doesn't agree with your interpretation of the fossil record and evolutionary history at all. Picture Japan's violent tsunami multiplied to a global scale, eroding away practically everything. The majority of the fossils and layered geological records then deposited as the turbulent ocean calmed down and the water receded from the land. The large flow of receding waters carved out river basins and canyons quite quickly from the soft sediments.
For someone with this world view, the "Facts" of evolution are not incontrovertible. The story of evolution, as derived from the fossil record, is based on assumptions that the creationist doesn't agree with.
That's not to say that the creationist disagrees with the facts of biology, as derived from examining living animals and how they change over time. It's the extrapolation of currently observed processes into the unknowable past that they disagree with.
Remember to delete history on that kiddos.
If this history makes it onto a disk, you've already lost.
Your program is sick! Shoot it and put it out of its memory.