Stock grouping
The stock grouping is the reduction in the number of shares in circulation, which are replaced by new shares according to a set ratio. At the same time, the price must increase in an inversely proportional way to the decrease in the number of shares.
For example, with a 1 for 2 stock grouping each shareholder is allocated 1 "new" share for each 2 "old" ones held: as a result, the number of shares in circulations for that company will be halved. Borsa Italiana calculates the adjustment coefficient according to formula 1. This value, always with 6 decimal digits, is multiplied by the strike prices (daily closing prices) and divided by the lot size.
Consequently, stock option contracts (stock futures) subject to a stock grouping will see a change in their strike prices (daily closing prices) and lot size.
Formula 1.
V
K = ------
N
where:
- V = number of old shares
- N = number of new shares
Impact on derivative contracts
Adjustment of the strike (daily closing price):
Eex = Ecum x K
where:
- Ecum = strike price (daily closing price) before the adjustment
- Eex = strike price (daily closing price) after the adjustment
Adjustment of the number of underlying shares (lot):
1
Aex = lot x -----
K
where:
- Aex = number of underlying shares (lot) after the adjustment
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Example
Stock grouping of the Finmeccanica shares, official notice n. 9253 of 7/13/2005
Description of the adjustment
Stock grouping of 1 new share for each 20 old shares.
Impact on derivatives contracts
With exclusive reference to the stock option contracts (futures) on Finmeccanica shares, the adjustment will affect both the strikes (daily closing price) and the number of shares (lot) underlying the stock option contracts (futures).
This intervention will be on the basis of the adjustment coefficient K, rounded off to the 6th decimal digit, as per the following example:
V
K= ----- = 20
N
where:
- V = number of old shares
- N = number of new shares
Adjustment of the strike price (daily closing price) and the number of shares underlying the stock option contract (future):
Eex = Ecum × 20
where:
- Ecum = strike price (daily closing price) before the adjustment
- Eex = strike price (daily closing price) after the adjustment
Aex = 10.000 × 1/20 = 500
where:
- Aex = number of underlying shares (lot) after the adjustment
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