There is two ways to look at a 1 share trade: 1) To bring the...

There is two ways to look at a 1 share trade:

1) To bring the price up or down can play a big part in changing the look of a candle in a chart. Some candles can entice certain traders to jump in a stock.

2) To benefit the buyer/seller that is making that 1 trade happen. As you have pointed out heaps of times when a 1 share trade goes down a pip the sellers are the ones that lose out and the buyers are on the winning side. Depending on how many units they are trying to sell/buy, but for each 100,000 units it is $500 in their favour/loss. The reverse happens when it goes up 1 pip. Buyers need to fork out more money and the sells get more than they bargained for.

The current minimum trade amount for TAS is 2857 units ($500 at 0.175). Normally the 1 trade will happen with many multiples of thousands, so the minimum trade in which you talk is not the case in most of the scenarios. But day to day trading where if a large holder is trying sell out and is dribbling out 36, 732, 12, 1012 at a time, yes I think we are all pissed off with that manipulation and should be outlawed. Though I would say the ASX would put up a view of if some large holder wishes to get out and just sell on market the share price would fall much more than it would if it were dribbled over a week or 2.

Those half pip trades are supposedly from best execution between the ASX and Chi-X. If you have the following market depth.

	Column 1	Column 2	Column 3	Column 4	Column 5
0	ASX Buy			ASX Sell
1	0.200	100,000		0.210	150,000
2	0.195	150,000		0.220	10,000
3	0.190	10,000		0.225	50,000
4
5	Chi-X Buy			Chi-X Sell
6	0.205	50,000		0.250	84,000
7	0.200	25,000		0.280	24,000
8	0.190	10,000		0.300	35,000

My interruption is, If someone wishes to sell 100,000 into the ASX 0.200 line 50,000 would be sold at 0.2025 and 50,000 at 0.20

The best execution policy sees that 50,000 is on offer a Chi-X, but instead of selling at 0.205 it gets sold at 0.2025 because someone is willing to sell at 0.20 and someone is willing to buy at 0.205, for the benefit of both holders it splits the buy/sell in the middle. So the seller gets more than what they wished for (was happy at 0.20, but got 0.2025) the buyer got it better than they wishes for (was happy to buy at 0.205, but got 0.2025)

Until all brokers combine the ASX and Chi-X into the one trading depth, we are always going to see this half pip discrepancy. Comsec has been saying its coming soon for the last 3 yrs but nothing has happened.

Not sure why they were invented, but I would hazard a guess, for those whom had not executed their whole order during the day, could amend their order to get it filled. Though you could pose the question, what stops them from just amending at 3:59pm?