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Q: Ebay Shill bidder ( Answered,   3 Comments )
Subject: Ebay Shill bidder
Category: Business and Money > eCommerce
Asked by: llgg-ga
List Price: $2.00
Posted: 01 Apr 2005 02:06 PST
Expires: 01 May 2005 03:06 PDT
Question ID: 503519
can I identify a shill bidder simply by looking at the bid history?
coz the bider search doesn't help much. for example, here is a case i
suspect: (sorry for the format. the parantheses is rating.)

bidder  price          time

	US $152.00	
winner(4)		9:15:03 PST
	US $149.50	
Bidder8 ( 73)		9:14:48 PST
	US $127.00	
winner(4)		9:11:19 PST
	US $115.00	
bidder4(1)		7:19:42 PST
	US $100.00	
winner(4)	7:19:22 PST
	US $100.00	
winner(4)		8:50:36 PST
	US $95.00	
winner(4)		8:50:03 PST
	US $92.01	
winner(4)		8:49:49 PST
	US $90.00	
winner(4)		8:45:30 PST
	US $85.00	
		6:07:54 PST
	US $80.00	
bidder4(1)		3:12:48 PST
	US $80.00	
bidder1		2:05:50 PST
 Bidder1	US $77.00	
		2:05:37 PST
 Bidder1	US $75.00	
		2:05:13 PST
Bidder2	US $66.75	
		1:10:08 PST
Bidder2	US $62.00	
		1:09:51 PST
	US $60.00	
bidder4(1) 	9:01:56 PST
Bidder8 ( 73	US $60.00	1:09:40 PST

bidder7(2)	US $49.00	08:11:24 PST
	US $47.00	
bidder7(2)		08:11:08 PST
	US $45.00	
bidder1(26)		16:17:43 PST
	US $45.00	
bidder1(26)		07:21:03 PST
	US $40.00	
		10:49:44 PST
	US $40.00	
bidder5(4)		16:17:30 PST
winner(4)	US $34.00	
		16:17:16 PST
	US $32.00	
bidder4(1)		16:17:04 PST
	US $30.00	
winner(4)		18:43:03 PST
	US $25.00	
bidder12(1)		13:37:13 PST
	US $24.00	
		12:59:21 PST
	US $21.00	
		13:14:42 PST
	US $20.00	
bidder14(1)		11:45:30 PST
	US $20.00	
		12:57:33 PST
	US $15.00	
		12:57:21 PST
	US $11.00	
		12:57:14 PST
	US $10.00	
		12:57:05 PST
	US $7.00	

Clarification of Question by llgg-ga on 01 Apr 2005 16:19 PST
Hi, politicalguru-ga, nope, i didn't report to ebay. i just suspect. i
checked the suspects on bidder search page, but it didn't find any
pattern. i'm actually interested in the products of a particular
seller, but by looking at that seller's history, i found many strange
biddings on his previously sold products. so i just want to make sure
i know what's going one when i bid.

myoarin-ga. by looking at the schedule, it's strange to me taht
bidder4 was not outbidded but he placed 4 consecutive bids to boost
the price from 10 to 20; bidder1's three consecutive bids: 75, 77, 80.
i can interprete the $75 he put in was to outbid the $65 at a large
amount. but why he then place another 2 bids ? at last, i dont' quite
understand what the winner was trying to: he place 3 bids to outbid
his own bid at $90 : $92, 95, 100.

Subject: Re: Ebay Shill bidder
Answered By: efn-ga on 01 Apr 2005 21:06 PST
Hi llgg,

In principle, I don't think you identify a shill bidder from the
history of a single auction.  There is not enough information there to
distinguish a shill from any other bidder.

I think I can explain the bids you found puzzling, as noted in your
clarification.  The key is to look at the times as well as the

For example, let's look at bidder6 raising the price from $10 to $20. 
If you just look at the prices, it looks like he is just bidding
against himself for no apparent reason.  (I will use male pronouns for
simplicity.)  But if you look at the time sequence, you can see that
first, bidder14 bid $20 at 11:45:30.  The previous high bid was $7, so
bidder14 would have shown as the high bidder at $7.50.  At 12:57:05,
bidder6 comes along and sees a minimum bid of $8.  He boldly bids $10,
but because bidder14 had bid $20, bidder6 is automatically outbid, and
the price goes to $10.50, with bidder14 still the high bidder.  The
minimum bid is now $11 and bidder6 decides the item is worth that to
him, so he bids $11.  Again, he is automatically outbid and the price
goes to $11.50 with bidder14 still high.  So bidder6 tries again with
$15 and is again automatically outbid.  So he tries $20, tying
bidder14's bid.  Now the price shows as $20 with bidder14 the high
bidder, because he bid that amount first.  Bidder6 can now conclude
that he has tied the high bid, so he bids $24 and becomes the high

So bidder6 was not pointlessly bidding against himself all this time,
he was bidding against bidder14 and finally outbid him.  This is
actually a common pattern on eBay.  It would be simpler just to decide
what an item is worth to you, bid that amount, and let the automatic
bidding work, but many people like to bid small increments repeatedly.
 It's not uncommon to see several bids from the same person a few
seconds apart, all losing.

The case of the winner bidding the price from $90 to $100 appears
similar, although the transcript looks a little fishy in showing two
$100 bids from the same person at different times.  But anyway, while
the winner was bidding the price up, he kept getting outbid by the
earlier $115 bid from bidder4.

The case of bidder1's bids from $75 to $80 does not fit this pattern,
but it is not necessarily suspicious.  bidder1 could have been
changing his mind about what the item was worth to him and increasing
his bid for protection from other bidders.

To identify shill bidders, I think you have to look at patterns across
multiple auctions.  If bidder A is always coming in second in seller
B's auctions, that would be suspicious.  (The idea of a shill is to
bid up the price and lose to a real bidder.)  If bidder A has no
history of ever buying anything else, that would be more suspicious. 
If bidder A bids on all of seller B's auctions and never bids on
anything else, that would be suspicious too.

For more on detecting shill bidding, see the last answer on eBay's
help page on the topic:

eBay says it is suspicious for a bidder to make repeated bids in small
increments when he is the high bidder.  As I said, you have to check
the times to determine whether a bidder is actually the high bidder
when he makes such bids, or he is bidding against a higher previous

I hope this explanation is helpful.

Subject: Re: Ebay Shill bidder
From: politicalguru-ga on 01 Apr 2005 02:45 PST
Have you reported that to eBay?
Subject: Re: Ebay Shill bidder
From: myoarin-ga on 01 Apr 2005 09:08 PST
One can set a bid on eBay that "kicks in" until the maximum of that
bid is reached.  That is, without following action online, such a bid
is an active participant, and thus, if other bidders drop out before
its maximum is reached, it gets the item.  (I'm no eBay expert, but
that is what I understood from reading the site once  - not just now,
so I may be wrong).
From your schedule, I could not see which bidder you thought was the shill.
I am told that it only is worth following an eBay item in the last minutes.
That could, of course, make it interesting for the seller to try to
boost the price (have the price boosted) in the earlier period so that
the bidding level at the end is at a higher leve.
Perhaps you can explain which bidder(s) in your schedule you think is/are shills.
Subject: Re: Ebay Shill bidder
From: air2air2-ga on 29 Apr 2005 22:31 PDT
I got hurt badly by a shill bidder and I think this is a serious
threat to eBay credibility - really scary stuff.  Here are sites that
you should watch out for:

Not a good experience at all.

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