https://www.amazon.com/Wisdom-Crowds-James-Surowiecki/dp/0385721706 All this got me to thinking... does this apply to coin grading as well? The recent NGC initiative where they'd offer a grade opinion based on a photo on Ebay really stuck with me. After all, this is literally what we do here on CoinTalk. How good are we compared to the "authority"? I looked at Guess the Grade threads on the US coins forum since April. I ruled out anything with less than 5 posts, and any details graded coin since those don't have standard grades. Turns out, there's been 31 GTG posts since April. So here's what I found. There were 6 GTGs with circulated coins, with 117 total guesses. This sample size is quite small, and will require revisiting in a few months to get more statistically reliable results. However, preliminary results are thus: The average TPG grade was 42.67, the average CoinTalk grade was 47.26. On average, CT overgraded by 4.6 points (in circulated grades, this corresponds to generally one increment higher - example, 40 vs. 45). Again, this sample size is generally too small to have reliable data. The widest spread was over 10 points off. I was actually rather surprised at the amount of error in the circulated grades, since these grades are largely determined by amount of wear. There are standardized references (such as Photograde, and the ANA grading guide) which show pictures of each coin in each grade. I am curious to see if this difference between CT and the TPGs changes with a larger sample size. For uncirculated coins, there are 25 GTGs with 369 total guesses. The average TPG grade was 64.7, the average CoinTalk grade was 64.26. This gives a difference of -0.45, meaning on average, CoinTalk slightly undergraded coins posted. This ranged from a 0.03 difference (meaning, CoinTalk nailed the TPG grade exactly) to a -3.15 difference, meaning CoinTalk significantly undergraded the coin compared to the TPG. I also broke this down into the most common types of coins for GTGs - Morgans, Buffalos, and Walkers. The results were fairly consistent among the types, although the Buffalo did have the biggest difference. I need more data to refine this area, and will post more details in my next update. The standard deviation of the error in the uncirculated coins between CT and the TPGs is 1.29. That means that the majority of CT guesses are within about a point of the TPGs. On average, CoinTalk was about a one point difference from the TPG - an acceptable margin in my opinion. What we find from this (admittedly small sample size) is that CoinTalk is generally fairly accurate in its grading. In many threads, there is a wide variance between the highest and the lowest grades, but on average we're pretty close. Some variables which will affect the CoinTalk grades include: photo quality, hidden surface issues, differences of opinion in eye appeal, grader experience, and difficulty in grading certain types of coins. There are a couple of lessons we can learn from this, especially for newer graders. I highly encourage all of you to participate in the guess the grade threads. You will learn to calibrate your grade to the accepted standard authority. However, if you find yourself more than about a point different from the TPG, you need to figure out why. Is there something you missed? Is there something that you graded too harshly? Is there something that you have a difference of opinion? Do you find a coin attractive or unattractive, and you weigh that too heavily compared to the objective qualities of the coin? These guess the grade threads are some of the most valuable threads on CoinTalk for these reasons - learning to grade coins is an essential skill for the collector. That is why I always try to explain and justify my grade rather than just throwing out a number - and I encourage you all to do the same in the interest of education. For the people who post GTG threads, there are also a few takeaways. Always strive to have the best pictures possible. Often, after several posts complaining of poor pictures, the poster will retake pics and the grades will shift significantly. This can be avoided, and yield more accurate results, if the pictures you post are high quality to begin with. I know you're excited to share your coin. I know you want to post the thread, and you're impatient. I get it, I do the same. But you also know that those pictures could be better... take the best pics you can before you post the thread and you'll get much better guesses. Also, you'll get a lot more guesses if you post a poll. The average number of guesses with a poll versus without is sometimes an order of magnitude higher - many, many people will click on a poll and never post a thing, rather than have to actually post a guess. The average grade guessed on these threads is usually more accurate. Give a wide range above and below your coin to offer an adequate variance of responses - but offering a poll generally gives much more accurate data. @Lehigh96 is particularly good at this, but few other posters regularly offer a poll on their GTGs. I realize now that we should. From a simply numerical perspective, CoinTalk does pretty good. I intend to continue this analysis for the next few months, and will update the boards once I have a larger sample size (I did this same study a couple of years ago, but didn't post it - the results were similar). If you want to learn how to grade more accurately, or understand the grading process, CoinTalk members can recommend some books and resources to assist your learning. You only have to ask. So, thoughts?