Overview
The BIT Portfolio Margin (‘PM’) tool evaluates the risk of a portfolio by calculating the most likely loss that could occur to a portfolio based on a series of hypothetical market scenarios and a number of parameters set by the risk management team. Compared to the regular margin methodology, which aggregates margin on the individual contract level, the PM methodology tends to reward hedgers by offering a greater margin benefit to their well maintained low risk portfolios. For speculators who have directional portfolios, however, lower margin is not always guaranteed with the PM enabled.
The calculated PM requirement allows for effective risk coverage whilst preserving capital efficiency. The final output of the margin model is used to directly collateralise margin requirements to help insure the positions of the members.
How to calculate PM?
The margin components for PM are scenario PnL and floor margin. Scenario PnL represents the core risk analysis of the PM model by simulating the portfolio’s hypothetical profit and loss under a specific set of market conditions. The BIT PM model consists of 33 scenarios which include underlying price up/ down movements and option up/ down volatility (see below).
In order to ensure minimum risk coverage for all possible combinations of instruments, the floor margin is set for both outright and options, which, to some extent, will help reduce the margin procyclicality for low risk portfolios.
An example:
Portfolio (underlying BTC):
1 BTC Long Perpetual (Price 9500 USD/ BTC)
2 BTC Short 20200828 9500 Call option (IV= 50%)
Scenario PnL component
Risk parameters:
Price range up 18%
Price range down 18%
30 day vol Volatility range up 0.45
30 day vol Volatility range down 0.28
Out of the 33 scenarios, underlying down -18% and standard 30d volatility up +0.45①generated the worst loss (approx. 0.2031BTC) for the above delta hedged portfolio on 24th July 2020 at 11:30 GMT+8.
Floor margin component
Risk parameters:
Outright floor margin - 0.50%
Option floor margin - 0.01 BTC
PM Initial margin ratio - 1.25
Outright floor margin total = Outright floor margin * Σ|Outright position| = 0.005 * 1 = 0.005 BTC
To calculate Option floor margin total, we
firstly calculate the Discounting factor (DF②) which aims to apply a higher discount to the charge of the options with strikes closer to the underlying, the discounted charge for each single option would be
Option floor margin (i) = DF(i) * QTY(i) * 0.01 BTC;
2. For all options per expiry, we group the instruments into two buckets:
1）Strike price>Underlying price
2）Strike price<=Underlying price;
3. Within the same bucket, we net sum the Option floor margin, and aggregate the charges from all buckets if occurred
Option floor margin Total=(|min{Σ[QTY(i)(bucket1))*DF(i)],0}| + |min{Σ[QTY(i)(bucket2))*DF(i)],0} |)* Option floor margin
Given the underlying price is 10000, Option floor margin Total = |-2 * 0.5 |* 0.01 = 0.01 BTC③
To sum up:
Portfolio Maintenance margin Total = Scenario PnL component + Floor margin component = 0.2181BTC
PM Initial margin Total = PM Maintenance margin Total * 1.255 = 0.2726 BTC
About the risk parameters
BIT employs a non-parametric approach as the main risk model to calculate the parameters. In order to ensure an overall conservative margin estimate, the risk team also employs a parametric approach for validation. Below demonstrates an overview of the BIT risk model.
The parameters will be calibrated periodically at the discretion of the BIT risk management team. And the model performance will be dynamically monitored on the instrument and portfolio level by the back-testing. Below shows an initial set of risk parameters dated 24th July 2020
Default Management
Once your account MM is breaching the total equity level, the auto-liquidation (default) procedure will kick off by adjusting your future positions as the first step, aiming to reduce the overall risk of the defaulter’s portfolio. Note that during the period of default, it is at the discretion of the exchange in terms of the further steps of positions handling.
How to have a PM account?
To be qualified for a PM account, below are the minimum criteria to be met:
Cash Balance>0.5BTC
The PM account holders must be able to demonstrate their experience in trading options and declare their understanding about Portfolio margin
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①Vol up change of the contract= (30/days to expiry) ^ 0.3 * 30d vol up change =(30/35) ^ 0.3 * 0.45
②DF(i) =min[ |K(i) - Price_Underlying)|/ (x* Price_Underlying),1]; x is currently set to be 10%
③If we have 2 BTC Short 20200828 9500 Call option and 1 BTC long 20200828 9750 Put option, both instruments belong to the same bucket and Option floor margin Total=|( -2 * 0.5+1*0.25)|*0.01 = 0.0075 BTC
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