Conspiracy Theories

There are some who believe in conspiracy theories, such idle ideas as the Plunge Protection Team and Zeitgeist.  Silly people.  I mean, other than the fact that the PPT exists, much of Zeitgeist has already occurred, and the DJIA has finished up on every Friday of 2013, i.e., 9 times in a row, there's really nothing to these silly ideas. 

Editorial Note: I added this additional information after the original post.... Perhaps you're saying to yourself, 9 Fridays in a row with the Dow Jones Industrial Average closing up on the day, is not really any big deal. It's merely coincidence. So let's look at this line of reasoning. First, the "gut check" approach. How often have you seen someone spin a single color (red or black) on a roulette wheel, 9 times in a row? It's entirely possible you have, but extremely unlikely unless you happen to work the roulette wheel at a casino, you're a degenerate gambler with a love for roulette, or perhaps a graduate student in mathematics. The actual likelihood of this occurring is the probability of a single occurrence, to tge power of the number of observations. So if the Dow is up half the time, down half the time, the probability is simply .5 for a single occurrence. With 9 Fridays thus far, the probability that the Dow would be up 9 consecutive Fridays is (.5)^9, which equals 0.001953125, which is simply 0.2%, which means that such an event randomly occurs, by chance, roughly 1 out of every 500 times (the actual number is 512, which is the solution of 2^9). To be more real world, one should account for the fact that over long periods, the stock market indices have a positive slope, which is to say, they tend to go up as a function of growth in the economy, population, and inflation, among other things. So, the probability of the market being up on a given day may be somewhat more than 50%. How much? Who knows? It's not critical for this example. I think a generous number to use is .60, while I think the right number is probably closer to .55. If one uses .60, the resulting probability is about 1%, five times larger but still not very likely to occur (i.e., it should occur one time out of 100 sets of 9 Fridays, all else being equal). You may want to note two footnotes to this footnote, fn^2 you could call them. One is that if you assume that up days have more magnitude than down days, then up days and down days could still be 50/50 and have a positive slope. Secondly, roulette is not a 50/50 proposition, since there are two green spots on the wheel, for 0 and 00. That's the casino's payout: 2/38 = 1/19 ~ 5% to the house, generally (also called the rake, or edge). Against a player betting a color, the casino's odds of winning are 20/38 ~ 53%.