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

TPI 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 a Psychic reader on a pawn, the pawn's TPI 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% TPI would have a TPI of 33% after installing the Reader, while this would be increased to 36% if they had 200% Psychic Sensitivity. To calculate your TPI from Psychic reader: Social skill level*0.015*0.1*Psychic Sensitivity.
Drug Use: Essential precept provides a +10% TPI only for selling drugs. Only social and hard drugs are affected, medical drugs like Luciferium and Penoxycyline do not receive the TPI improvement. Flat bonus, cannot be modified or modify other bonuses.
Ranching: Central precept provides a +10% TPI only for selling animal products. Despite saying "animal products", this TPI change applies only to meat, leather and wool. Eggs (fertilized or not), milk and insect jelly are not affected, while both human meat and human leather are. Live animals are not affected. Flat bonus, cannot be modified or modify other bonuses.
Giving the leader role to a pawn provides a +2% TPI. Flat bonus, cannot be modified or modify other bonuses.
Trading with others faction’s settlement via caravan provides a +2% TPI. Flat bonus, cannot be modified or modify other bonuses.
Inspired trade provides a +18% TPI. Flat bonus, cannot be modified or modify other bonuses.

TPI is not affected by pawn beauty, nor Social Impact buffs such as from the bowler hat. The formula for calculating the buy price modifier(i.e the percentage of the item's value you will pay) is $buy price modifier = 60%*(100%+TPI)$ .The equivalent formula for the sell price modifier is $buy price modifier = 140%*(100%-TPI)$ .

^[1]

Social Skill	TPI	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%
21	31.5%	78.9%	95.9%
22	33.0%	79.8%	93.8%
23	34.5%	80.7%	91.7%
24	36.0%	81.6%	89.6%
25	37.5%	82.5%	87.5%
26	39.5%	83.7%	84.7%
27	41.0%	84.6%^[1]	82.6%
28	43.0%	85.8%^[1]	79.8%

↑ ^1.0 ^1.1 ^1.2 Note that the actual sell price will be lower than what is listed because the sell price of an item cannot be larger than its buy price.

How to calculate TPI

The TPI is calculated as follow:

Base value: 100%
Social: *(Skill level*1.5)%
Talking: if inferior at 95%: *(Talking ability with 90% weight)% | else: *100%
Hearing: if inferor at 80%: *(Hearing ability with 90% weight)% | else: *100%
If has a psychic reader: *(10%*psychic sensitivity)
If has Inspired trade: +18%
If is colony leader: +2%
If trade with settlement: +2%
If relevant precept: +10% (selling only)

To use this calculation, convert the % value of the game by multiplying it by 0.01.

The calculation for TPI is : [SL]*1.5*(1*(0.1+0.9*([T]/0.95))*(1*(0.1+0.9*[H]/0.8)*(1+(0.1*[PS]))+[IT]+[L]+[TS]+[P]

Multiply by 100 if the value is wanted in %.

Variable	SL	T	H	PS	IT	L	S	P
Meaning	Social Level	Talking Ability	Hearing Ability	Psychic Sensitivity	Inspired Trade	Leader	Trade with Settlement	Precept
Used If	Always	Has T<95% else 0.95	Has H<80% else 0.8	Has psychic reader	Has inspired trade	Is leader	Is trading with settlement	Has relevant precept and is selling

Trade Price Improvement Milestones

The list below shows the milestones of TPI:

The minimum TPI a pawn can have is 0%.
A TPI 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 TPI than 40% means 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 TPI 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 TPI 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 TPI 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% TPI 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% TPI at a Social skill of 20.

Getting a TPI of 40% with 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% TPI.

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

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

Numbers in Trades

When you trade, your TPI in the top left corner is rounded to the nearest integer. To see the real TPI that is used for calculation, check the information tab of the pawn.

When trading with others faction’s settlement, the TPI in the top left corner will not include the 2% TPI 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