Slippage KYU hota hai: ek market orderspeed ka vaada karta hai, price ka nahi. Woh book mein upar (ya neeche) march karta hai, har level ke available shares khata jaata hai jab tak tumhari quantity fill na ho jaye. Agar tumhara order top level se bada hai, toh baad ke shares worse prices pe fill hote hain → average fill price quote se door drift karti hai.
Partial fills KYU hote hain: ek limit orderprice ka vaada karta hai, completion ka nahi. Agar itne counterparties nahi hain jo tumhari limit pe (ya usse better) trade karna chahein, toh sirf available portion execute hota hai; baaki book pe rest karta hai ya cancel ho jaata hai (order flags jaise IOC/FOK ke hisaab se).
Scratch se derive karna (average kyun, last price kyun nahi?): Tum har chunk ko uske apne level ke price pe pay karte ho. Total cost price×size ka sum hai. Ek single quoted number se compare karne ke liye tumhe ek representative price chahiye — size-weighted mean, kyunki ek level pe bada chunk doosre level ke tiny chunk se zyada count karna chahiye. Woh exactly pˉ=∑piqi/∑qi hai. Slippage phir bas "woh weighted mean jahan maine aim kiya tha wahan se kitna drift hua" hai.
Sell market order mein tum bids ko downward khate ho, isliye S=p0−pˉ (tum quote se kam receive karte ho).
Socho ek candy shop. Sign likhta hai "candy ₹5". Lekin ₹5 pe sirf 3 candies hain, phir 4 candies ₹6 pe, phir aur ₹7 pe. Agar tumhe 8 candies chahiye, sab ₹5 mein nahi milenge — tum saste waale scoop karte ho, phir baaki ke liye zyada pay karte ho. Tumhara average price sign se zyada ho jaata hai: woh extra bit slippage hai. Aur agar tumne dukandaar se kaha "main ₹5 dunga, ek rupya zyada nahi," toh tumhe sirf 3 candies milti hain — woh partial fill hai; baaki 5 tumhe milti hi nahi.
Expected/reference price aur trade ke actual average execution price ke beech ka difference.
Partial fill kya hota hai?
Jab sirf tumhari ordered quantity ka kuch hissa execute ho, baaki unfilled reh jaaye (resting ya cancelled).
Market orders slippage kyun cause karte hain?
Woh speed aur completion ko priority dete hain, isliye book mein upar/neeche walk karte hain aur progressively worse prices pe multiple price levels khate hain.
Limit orders partial fills kyun cause karte hain?
Woh price cap karte hain, isliye sirf tumhari limit pe (ya better) available quantity execute hoti hai; baaki limit violate kiye bina fill nahi ho sakti.
Average execution price ka formula?
pˉ=∑iqi∑ipiqi — filled chunks ka size-weighted mean.
Nahi — woh favorable/negative bhi ho sakti hai agar fill se pehle market tumhari direction mein move kare.
Slippage aur bid-ask spread mein difference?
Spread top-of-book round-trip cost hai; slippage woh extra drift hai jo top-of-book ke paar walk karne se hoti hai jab tumhari size available liquidity se zyada ho.
IOC order unfilled quantity ke saath kya karta hai?
Abhi jo available hai woh lene ke baad use immediately cancel kar deta hai.
