Offer your thoughts or opinion on the input financial query or topic using your financial background.

Why does a stock price drop as soon an I purchase several thousand shares at market price?
Unless you are buying millions of dollars worth of a stock at a time, your transaction is a drop in the bucket, unlikely to have any noticable effect on the stock price. As Ian says, it's more likely that you are just remembering the times when the price dropped after you bought. If you keep careful track, I suspect you will find that the price goes up more often than it goes down, or at least, that the stocks you buy go up as often as the average stock on the market goes up. If you actually kept records and found that's not true, the most likely explanation is bad luck. Or that someone has placed a voodoo curse on you. I suppose one could imagine other scenarios. Like, if you regularly buy stock based on recommendations by well-known market pundits, you could expect to see a temporary increase in price as thousands or millions of people who hear this recommendation rush to buy, and then a few days or weeks later people move on to the next recommendation, the market setttles down, and the price reverts to a more normal level. In that case, if you're on the tail end of the buying rush, you could end up paying a premium. I'm just speculating here, I haven't done a study to find if this actually happens, but it sounds plausible to me.