11/12/2025
Credit to Heather Renee
Understanding COI and AVK
What They Mean and How They’re Calculated on K9-Data
Someone asked this earlier, so I wanted to address what these calculations mean. There has been a lot of talk about COI and AVK, but what do those numbers actually mean, and how are they calculated? Here’s an overview for anyone who wants to understand what these calculations really tell us about a pedigree.
COI (Coefficient of Inbreeding)
A calculated COI is an estimate of how closely related a pedigree is. It represents the probability that, at any random point in a dog’s DNA, the two copies of a gene segment inherited from the sire and dam came from the same ancestor.
In other words, it predicts how much of a dog’s genetic material could be identical because of shared ancestry. COI doesn’t analyze specific genes. It’s a mathematical estimate taken across the entire pedigree (in our case, up to 12 generations).
A COI of 0% indicates there were no common ancestors found within the generations analyzed. A COI of about 12.5% is what you’d expect from a half-sibling mating. The higher the COI, the more repeated ancestry there is in the pedigree.
How It’s Calculated
K9-Data uses Wright’s Coefficient of Inbreeding, developed in 1922. It remains the standard method for calculating inbreeding from pedigrees.
Here’s how it works:
The program scans each dog's pedigree for ancestors that appear on both the sire’s and dam’s sides.
It measures how far back those shared ancestors occur. The closer they are, the more impact they have. This concept helps explain why distant ancestors contribute less to the final COI.
It sums up all of those contributions to produce the total COI percentage.
The closer and more often an ancestor repeats, the higher the COI. A half-sibling mating produces about 12.5%, while a distant overlap may add only a fraction of a percent.
Lower COI indicates less shared ancestry and a lower probability of identical genes being inherited from common ancestors, while higher COI reflects more repeated ancestry and a greater likelihood of shared alleles.*
COI Contributors
When you see “Top ancestors contributing to COI, in order of influence” on a dog’s page, those are the specific ancestors that most impacted the COI calculation. Each one shows which ancestor it is and how much of the total COI they contribute.
If one or two ancestors make up most of the COI, the pedigree is tightly focused on those lines. If the percentages are spread across many ancestors, the inbreeding is more distributed.
AVK (Ancestor Loss Coefficient)
AVK looks at the pedigree from the opposite direction. Instead of measuring overlap, it measures how many unique ancestors exist compared to how many there could be.
Each generation doubles the expected number of ancestors: two parents, four grandparents, eight great-grandparents, sixteen, thirty-two, sixty-four, and so on. AVK compares how many of those ancestors are unique dogs versus repeats.
For example, if a twelve-generation pedigree could have 8,190 unique ancestors but only 6,142 are unique, the AVK is 75%. That means roughly one-quarter of the ancestor “slots” are filled by dogs that appear more than once.
A higher AVK means more unique ancestors and a broader ancestry base. A lower AVK means more repetition and a narrower base within the generations included in the calculation.
COI vs AVK Contributors
COI contributors are the ancestors that appear on both the sire’s and dam’s sides. These overlaps create the inbreeding loops that raise a dog’s COI and show which specific ancestors are duplicated and how much each contributes to the total inbreeding.
AVK contributors, on the other hand, represent all of the unique ancestors within the analyzed generations. Each ancestor is counted only once, no matter how many times it appears. AVK reflects the overall variety of the pedigree, while COI highlights where that ancestry overlaps.
Some ancestors can influence both numbers. For example, when a dog appears multiple times in a pedigree, it reduces the number of unique ancestors (lowering AVK). If those repeats occur on both the sire’s and dam’s sides, they also form inbreeding loops (raising COI). Together, these two values describe both the breadth and the concentration of a pedigree.
In the AVK contributor table (the blood percentage table), each ancestor’s record shows their overall mathematical influence across the pedigree, even if they appear only on one side. Each ancestor is counted once, and the percentage reflects how much of the pedigree’s structure traces back to that dog. The record also includes how many times the ancestor appears and whether those appearances are on the sire’s side, the dam’s side, or both. These counts show how that ancestor’s influence is distributed throughout the pedigree and which lines dominate overall, even if they aren’t part of any direct inbreeding loops.
In short:
COI shows where the lines converge.
AVK shows how wide the pedigree base is within the calculated generations.
COI focuses on tightness, while AVK reflects breadth.
Accuracy and Data Quality
COI is based entirely on pedigree data, not DNA. Any missing or incorrect ancestors affect the results. Calculations run in weekly batches, so updates may take a short time to appear after pedigree edits.
Incomplete pedigrees can make a COI appear artificially low and AVK appear artificially high. The more complete the pedigree, the more meaningful the numbers. That is why we measure completeness and display that prominently.
Pedigree COI vs Genetic COI
Even full siblings don’t share identical genetic COIs because each puppy inherits a different mix of genes from its parents. That’s why pedigree COI can’t show an individual dog’s exact level of genetic inbreeding. It only predicts the average expected level for dogs from that pedigree. What it does show is which ancestors are repeated, how closely they’re related, and where the concentration of ancestry comes from.
No matter how many generations we calculate, pedigree COI will always be a statistical estimate based on relationships in the family tree. It’s not a direct measurement of the dog’s DNA. It tells us what the pedigree predicts, not what the genome contains.
At the same time, a genetic COI by itself doesn’t tell the full story. Without the mathematical pedigree COI, you can’t see why a dog’s genetic inbreeding is high or low, or which ancestors contributed to it. The pedigree COI explains the structure behind the numbers, while the genetic COI shows the outcome in that individual dog. Viewed together, they give both the story and the result of a dog’s COI.
Generation Depth
In theory, COI can be calculated for twenty or even thirty generations.
But mathematically, by the twelfth generation, a single ancestor contributes less than one forty-thousandth of a dog’s makeup. That influence is so small it no longer has a measurable effect on the result. Beyond that depth, the same historical founders begin to appear repeatedly under different names. Every modern Golden Retriever eventually traces back to the same limited group of foundation dogs, so extending the calculation further mostly repeats those same paths rather than revealing new information.
Adding more generations also increases the computational load exponentially. Each generation doubles the number of possible ancestor paths, resulting in millions of calculations for a single pedigree. This makes the process slower and more resource-intensive without adding much information.
Twelve generations strikes the right balance. It captures more than 99.9 percent of the pedigree’s calculated ancestral influence, minimizes noise from distant founders, and keeps the results efficient and easy to interpret.
In the future, we plan to offer the ability to calculate beyond twelve generations for users who want them. However, past that point the additional data tends to add more complexity than clarity. Once the same founders appear repeatedly, the extra depth becomes more theoretical than practical for understanding a modern pedigree.
Summary
COI is a statistical measure of how tightly related a pedigree is and how much repetition of the same ancestors occurs.
AVK (Ancestor Loss Coefficient) shows how broad the overall pedigree base remains by comparing unique ancestors to the total possible within the analyzed generations.
Neither number is good or bad on its own; together they describe the structure of a dog’s ancestry.
When we combine pedigree COI, genetic COI, and AVK with a deep understanding of the breed, we can make the best decisions for the future of our dogs, balancing health, type, and purpose in every generation.
