Trade Price Improvement

Trade Price Improvement is a stat: When this person acts as a trade negotiator, buy and sell prices are improved by this percentage. Its default value is 100%.

Factors

It is affected by the following:

Social: 0% plus 1.5% per skill level.
Talking: 90% weight, allowed defect of 0.05 and a max at 100%, meaning improvement over 95% does not affect trade prices.
Hearing: 90% weight, allowed defect of 0.20 and a max at 100%, meaning improvement over 80% does not affect trade prices.
Upon installing Psychic reader on a pawn, the pawn's T.P.I. increased by 10% of its current value, multiplied by the pawn's Psychic Sensitivity. That is, a pawn with Psychic Sensitivity of 100%, Social 20 and a resulting 30% T.P.I. would have a T.P.I. of 33% after installing the Reader, while this would be increased to 36% if they had 200% Psychic Sensitivity. To calculate your T.P.I. from Psychic reader: Social skill level*0.015*0.01*Psychic Sensitivity.
Drug Use: Essential precept provides a +10% T.P.I. ONLY for selling drugs. Only social and hard drugs are affected, medical drugs like Luciferium and Penoxycyline do not receive the T.P.I. improvement. Flat bonus, cannot be modified or modified other bonuses.
Ranching: Central precept provides a +10% T.P.I. ONLY for selling animal products. Despite saying animal products, this T.P.I. change only apply to meat, leather and wool. Egg, fertilized or not, milk and insect jelly are not affected while human leather and human meat are. Live animals are not affected. Flat bonus, cannot be modified or modified other bonuses.
Giving the leader role to a pawn provide a +2% T.P.I.. Flat bonus, cannot be modified or modified other bonuses.
Trading with others faction’s settlement via caravan provide a +2% T.P.I.. Flat bonus, cannot be modified or modified other bonuses.
Inspired trade provide a +18% T.P.I.. Flat bonus, cannot be modified or modified other bonuses.

It is not affected by pawn beauty, nor Social Impact buffs such as from the bowler hat.

Social Skill	T.P.I.	Sell Price	Buy Price
0	0.0%	60%	140%
1	1.5%	60.9%	137.9%
2	3.0%	61.8%	135.8%
3	4.5%	62.7%	133.7%
4	6.0%	63.6%	131.6%
5	7.5%	64.5%	129.5%
6	9.0%	65.4%	127.4%
7	10.5%	66.3%	125.3%
8	12.0%	67.2%	123.2%
9	13.5%	68.1%	121.1%
10	15.0%	69%	119%
11	16.5%	69.9%	116.9%
12	18.0%	70.8%	114.8%
13	19.5%	71.7%	112.7%
14	21.0%	72.6%	110.6%
15	22.5%	73.5%	108.5%
16	24.0%	74.4%	106.4%
17	25.5%	75.3%	104.3%
18	27.0%	76.2%	102.2%
19	28.5%	77.1%	100.1%
20	30.0%	78%	98%

How to calculate T.P.I.

The T.P.I. is calculated as follow:

Base value: 1
Social: *(Skill level*0.015)
Talking: if inferior at 95%: *(Talking ability with 90% weight)% | else: *1
Hearing: if inferor at 80%: *(Hearing ability with 90% weight)% | else: *1
If has a psychic reader: *(0.1*psychic sensitivity)
If has Inspired trade: +0.18
If is colony leader: +0.02
If trade with settlement: +0.02
If relevant precept: +0.1 (selling only)
Mutiply by 100 to get the value in %.

Trade Price Improvement Milestones

The list below shows the milestones of T.P.I.:

The minimum T.P.I. a pawn can have is 0%
A T.P.I. of 40% is the maximum value you should aim for selling stuff since the game prevents the selling price from being higher than the purchase price, so a higher T.P.I. than 40% mean selling for less. (This is the point where the selling price is equal to the buying price, 84% of the market value)
Without DLCs the maximum T.P.I. a pawn can have is 50% by having a Social skill of 20 (+30%), a Inspired trade (+18%) and trading with another faction’s settlement (+2%).
A T.P.I. of 64.23% is the highest value you can reach in the game with DLCs. To achieve this value you need a pawn with Social skill of 20 (+30%), a Inspired trade (+18%), the leader role (+2%), the implants Psychic reader (+3%) and Psychic sensitizer (+0.75%), the Psychically Hypersensitive (+2.4%) trait, a Legendary Eltex staff (+2.25%), Eltex skullcap (+1.8%), Eltex robe (+0.9%), Eltex vest (+0.69%) and Eltex shirt (+0.45%) and go on a caravan to trade with a settlement (+2%).
A T.P.I. higher than 100% is useless since the minimum buying price is $0.50.

Maximizing Trade Price Improvement

The Trade Price Improvement can only be maximize by installing Psychic reader on your pawn and improving it's Psychic Sensitivity since you are stuck at 30% with only the Social skill.

An easy way to get to 40% T.P.I. is to use a pawn with a burning passion for Social and the Psychically Hypersensitive trait. Then you need to assign this pawn as your leader and buy/find a Psychic sensitizer, a Psychic reader, a good Eltex staff and an excellent Eltex shirt to get exactly 40% T.P.I at a Social skill of 20.

Get a T.P.I. of 40% whit a Social skill lower than 20 is really difficult, as example a pawn with a Social skill of 18 need the leader role, the Psychically Hypersensitive trait, the implants Psychic sensitizer and Psychic reader, a Legendary Eltex staff, Eltex skullcap, Eltex robe, Eltex vest and Eltex shirt to get exactly 40% T.P.I..

With the Drug Use: Essential precept or Ranching: Central precept, you can technically sell items at a T.P.I. higher than 40% since there +10% T.P.I. are not counted toward the "selling price not being higher than the buying price" cap. Even if a T.P.I. of 50% is unreachable because maths, a T.P.I. of 47% is achievable and shoud be aim for as it is the new equilibrium between the buying and selling prices. This 47% T.P.I. is achievable by geting a colonist to a T.P.I. of 37%, by using informations of this page, and trading items affected by the precept of your Ideoligy.

If you manage to get a T.P.I. higher than 40% you can literally get everything traders haves for free. As an example, all traders buy Insect jelly, so you can sold it for $6.72 a piece at 40% T.P.I. then buy it back at $6.50 a piece with a T.P.I. of 42%.

Numbers in Trades

When you trade, your T.P.I. in the top left corner is rounded to the nearest integer. To see the reel T.P.I., that is use for calculation, go in the information tab of the pawn.

When trading with others faction’s settlement, the T.P.I. in the top left corner will not include the 2% T.P.I. improvement for this type of transaction despite being correctly count.

The price of items shows went trading in rounded to the nearest integer or the second decimal if the price in lower than $10, but the exact value is use for the total price calculation. For example buying Insect jelly with a Social skill of 0 will show a price of $11 even if the game use the exact price (8*1.4=$11.20) so buying 3 Insect jelly will cost $34 instead of $33 as the total price of a trade is always rounded to the nearest integer.

Version history

0.17.1546 - spread made much wider, but social skill also has a much greater effect on it.
1.1.0 - Trade price improvement from negotiator is now reported on the trade screen.

Stats