What is a spin-off?
A spin-off is a corporate action in which a parent company separates a subsidiary or business unit into a new, independently traded public company. Existing shareholders of the parent receive shares of the new entity, usually pro-rata, without paying anything. After the distribution date there are two listed tickers where there was previously one.
Spin-offs differ from divestitures (which sell the unit to a third party for cash) and from carve-outs (which sell a minority IPO stake while the parent keeps control). In a full spin-off the parent retains 0% of the spun-off entity after the distribution.
Mechanics on the distribution date
On the ex-distribution date three things happen simultaneously: (1) the new entity starts trading under its own ticker; (2) parent shareholders are credited shares of the new entity in their brokerage account at a fixed ratio (e.g. one new share for every five parent shares); (3) the parent share price drops by the implied value of the spun-off business — because that value has literally left the parent's balance sheet.
Total dollar value across the two tickers, summed for one shareholder, is unchanged the moment the distribution settles. You do not get richer or poorer on the ex-date. What changes is the unit of accounting: one position becomes two.
Why the parent's historical chart needs adjustment
If you compare the parent's closing price the day before the distribution to the opening price the day after, you will see a step-down that does not correspond to any news or earnings event. To keep long-term return calculations consistent, data vendors apply a corrective ratio so that the pre-distribution price multiplied by the ratio equals the post-distribution price.
That corrective ratio is recorded in the same split-history table as ordinary stock splits — it has the identical math signature. Whenever you see a ratio with an unusually large denominator (e.g. 1000:983, 5000:4912, 2000:1973), it is almost always a spin-off chart-stitching factor, not a real share-count change.
Worked example — Disney 2000:1973 (June 13, 2007)
Disney spun off its ABC Radio network on June 13, 2007 and merged it into Citadel Broadcasting. Existing DIS shareholders received Citadel shares; the DIS share price opened slightly lower on the ex-distribution date. Vendors record the adjustment as 2000:1973 — an effective multiple of about x1.0137. This is the price-continuity factor needed to glue the chart, not a real share-count event. Your DIS holding did not jump by 1.37% on June 13, 2007 — you simply received a small amount of Citadel stock alongside unchanged DIS shares.
Related concepts
- Stock split ratios explained — full taxonomy of every ratio you can encounter, including the spin-off chart-stitching family.
- Cumulative split multiplier explained — how spin-off ratios feed into the overall multiplier on a stock's history.
- Stock splits methodology — exact formula used for cumulative multiples and pre/post split prices.
To inspect the split & spin-off history for any company, browse the company directory and open the "Stock split history" tile.