Walmart has never reported any specific numbers about the marketplace GMV (gross merchandise volume in $), or the portion of walmart.com sales by marketplace sellers. The closest thing we got was the mention of "US e-commerce sales and GMV increased 29.0% and 36.1%" in the last quarter's earnings report.
Since Walmart marketplace has been receiving a lot of attention from marketplace sellers, we decided to investigate how big the opportunity of selling on Walmart really is.
We found one way to look at it - by comparing seller feedback. By comparing all feedback received by all Amazon.com sellers, to all feedback received by all Walmart sellers, we could get a relative number.
We are aware that the percentage of Walmart customers leaving feedback is different than that on Amazon.com. But at the moment, this is the best we can do. The results are highly speculative and might not be accurate.
By comparing feedback received, we found that today Walmart marketplace is roughly 1 percent of Amazon.com marketplace. For every feedback review on Walmart, Amazon.com sellers get 100.
This might not seem like a lot, but we also found that it has been growing at a steady pace since May when we first started tracking Walmart. In May it was just 0.2 percent (for every feedback review on Walmart, Amazon.com sellers got 500).
This doesn't directly equate to merchandise volume, but is a good rough estimate.
On Amazon marketplace sellers account for 50 percent of sales, but the marketplace has also been around for many years, and has a lot of services to offer. Walmart marketplace only started to grow last year, so there is a lot more growth in the future.
Number of sellers on the Walmart marketplace has been growing at a steady pace and just recently passed 10,000. Which suggests that as more sellers join the marketplace, the marketplace itself grows too. Both the number of sellers and the total feedback number has been growing at a linear pace.
The results of this experiment suggest that the marketplace is growing, and that there are many untaped opportunities, since new sellers increase total feedback received.