Are stock market events in GTAV scripted?
It seems that the assassination missions Lester gives to Franklin, beginning after the first heist, are the most obvious scripted occurances of stock market fluctuation. Most of these affect LCN, but some are companies on BAWSAQ.
Before each mission, invest in the target's competitor, ideally with multiple characters.
The missions are as follows:
- Hotel Assassination -- invest in BettaPharmaceuticals.
- Redwood Cigarette Assassination -- invest in Debonair Cigarettes.
- Vice Assassination -- invest in Fruit.
- Bus Assassination -- invest in Vapid after the mission. The stock will fall, but then rise again.
- Construction Assassination -- invest in Gold Coast.
Also, there is a random encounter in which you take a gentleman in a suit to the airport. If you get him there on time, he'll tell you to invest in Tickled on the BAWSAQ market. Doing so is a good idea, as this stock will climb rapidly for some time.
Additionally, as noted by other answers, performing actions against a company may increase the value of it's competitors. Examples given include destroying FlyUS planes in order to improve the stock of AirEmu and vice versa. The rivals of a company are summarised well in this answer to another question. However, I've not seen this actually work and fear it may just be a rumour at the games release that has been repeated so many times that everyone accepts it for truth.
There are basically two stock markets
- Liberty City National Exchange
- BAWSAQ
The first one is controlled by the game and it floats depending on internal game mechanics like missions. For example,
during some missions you have to kill a key person of a company. If, before doing that, you invest in the opposing company you will earn quite some money because after the mission the price of your stocks will sky rocket
The BAWSAQ is affected by how other players are playing GTA V online. It should fetches data from the Rockstar Social Club. For example:
BAWSAQ shares are influenced by the general Grand Theft Auto V community so as players purchase more weapons and armor, or add new mods, shares in Ammu-Nation and Customs increase.
For more information about markets mechanics in GTA have a look at this good article