Ultimately a company (that is listed on an exchange, or privately held) maintains a register of share holders. Sometimes they issue a certificate to the holders if they desire.
They may allocate some of those shares (e.g. from investors who have purchased their stock through brokers) in "street name", where the shares are registered to the brokerage firm on behalf of their client rather than the individual client.
In the US brokers clear their stock trades through DTCC and are required to segregate their customers stock positions from their own assets, so if they go out of business the customer's stocks are protected from creditors. If there was any impropriety (e.g. not segregating customer's stocks), SIPC insurance steps in.
In the US, the regulators are:
- The Securities and Exchange Commission (the Federal agency created by congress)
- The Self Regulatory Agencies (SROs):
- Any exchange that the broker is a member of (e.g. NYSE, NASDQ, Arca, BATS, etc.)
- FINRA (formerly the National Association of Securities Dealers)
Each has their own rulebook and conducts periodic audits of their members.
So where are [the owners of a stock] stored?
On the company's register of shareholders, and at the broker on their customer account records that are required to follow their SRO and SEC data retention policies, and the customer's statements.
is there some regulatory agency that keeps track of that?
The company keeps track of which investors and brokers own shares. The broker maintains records of which customer owns which shares. In the coming months all brokers are required to report which transactions or orders relate to which customer accounts in the Consolidated Audit Trail. This is information that will be accessible to all interested regulatory parties.
Or it is just a piece of a data in some GSTA database?
It is in the broker's database, and the broker is required by law and SRO rules to provide you with trade confirmations and statements.
could [I] lose it if GSTA went out of business or lost all their data?
If you kept your statements and trade confirmations, that would be evidence that you held the stocks. The trustee in bankruptcy would be responsible for gathering all the necessary information to give your stocks back to you.
If there was impropriety then SIPC insurance would step in.
And how are stocks moved into/out of the GSTA exchange?
The securities are only issued when a stock is listed - i.e. when the company goes public. Those that are held in street name generally remain in street name as they are traded among investors and brokerage firms. Typically the brokers maintain accounts with a central counter-party e.g. NSCC so when a trade has occurred, the selling broker's position in their NSCC account is decreased and the purchasing broker's position is increase.
