diff --git a/bsip-0034.md b/bsip-0034.md new file mode 100644 index 0000000..1635b38 --- /dev/null +++ b/bsip-0034.md @@ -0,0 +1,104 @@ + BSIP: 0034 + Title: Always Trigger Margin Call When Call Price Above Or At Price Feed + Author: Abit More + Status: Draft + Type: Protocol + Created: 2018-02-18 + Discussion: https://github.com/bitshares/bitshares-core/issues/606 + Replaces: - + Worker: To be done + +# Abstract + +Currently, in BitShares, a short position may be margin called only when both +two requirements are met: +* call price is above or equal to median price feed +* no limit order on the book is buying collateral with price higher than the + short position's call price + +This behavior has led to certain confusion and anger among market participants. + +This BSIP proposes a new behavior to improve the situation: drop the second +requirement, trigger margin call when the first requirement is met. + +# Motivation + +To avoid ambiguity, in this article, all prices are in terms of +`debt asset / collateral asset`, aka how much debt asset per collateral +asset. A bid is an order to buy collateral asset with debt asset. + +Generally, a short position may be margin called when its collateral ratio is +below or equal to maintenance collateral ratio (MCR). + +However, to calculate collateral ratio, a fair collateral price is needed. + +In BitShares, there are two data sources can be used to decide the fair +collateral price: +* the internal market +* the price feeds + +Currently, both data sources are used. Specifically, collateral price is decided +as the higher one between the highest bid price on the internal market and the +median price feed. That said, when a short position's collateral ratio has +fallen to below or equal to MCR according to median price feed (in this case, +call price of the short position is above or equal to median price feed), if +there is a bid on the market with high price, the short position won't be margin +called. + +This mechanism has led to certain confusion and anger among market participants. +* there are often orders with overlapping price on the book but didn't fill +* there are often short positions selling collaterals with low prices, but + traders are unable to buy at those prices +* it often causes borrowers to sell collaterals at a low price when have chances + to sell at higher price +* market manipulators / arbitrage traders have more chances to force borrowers + to sell collaterals at lower price + +This BSIP effectively proposes a new behavior: derive the fair collateral price +only from price feeds. + +# Rationale + +Since price feeds are provided by a set of chosen producers, the median price +feed is usually considered trustworthy. On the other hand, instant market +price is not as reliable, especially for the markets with poor depth, so it's +a rather limited supplement for calculating collateral price. + +At this moment, changing the rule to only use median price feed will clear away +the confusion the end users may have, while still keeping the derived collateral +price fair to an extent. + +After this change is done, placing a new limit order will no longer trigger a +margin call, cancelling a limit order or expiring a limit order will no longer +trigger a margin call as well, that means we don't need to check for new margin +calls nor black swan events in those scenarios, so we'll gain a side benefit on +performance. + +# Specifications + +In `check_call_orders(...)` function of `database` class, when matching a call +order with a limit order, there is a check: +`if( match_price > ~call_itr->call_price )`, when the result is `true`, +processing will be ended and `margin_called` will be returned. +Need to skip the check and the following `return` action. + +In `do_apply(...)` function of `limit_order_cancel_evaluator` class, and +similar code blocks after a limit order object is removed, no longer need to +call `check_call_orders(...)` function of `database` class. + +# Discussion + +[to be added if any] + +# Summary for Shareholders + +[to be added if any] + +# Copyright + +This document is placed in the public domain. + +# See Also + +* https://github.com/bitshares/bitshares-core/issues/606 +* https://bitsharestalk.org/index.php?topic=25926.0