(FORTUNE Small Business) -- Monday marked the start of a week-long eBay (EBAY, Fortune 500) boycott organized by sellers outraged at the auction site's recent fee and policy changes - an effort whose success will be hard to gauge until later in the week.

Third-party industry tracking sites, such as medved.net and PowerSellersUnite.com, show that live auction listings on eBay.com have dropped about 3% since the strike's Monday kickoff, from 14.5 million to around 14 million items.

But small swings in eBay's listings totals can be hard to interpret. The site's listings often fluctuate by several million items due to normal seasonality, and eBay further muddied the waters this week by running a one-day promotion last Wednesday offering highly discounted listing fees. That promotion immediately spiked the site's listings by more than 20 percent; since eBay auctions can run for up to 10 days, the special offer continues to inflate eBay's auction totals.

EBay spokesman Jose Mallabo declined to comment on third-party statistics, and said that the site's internal statistics show that the boycott "hasn't had an impact on our listings." EBay does not publicly release its listings totals

Some departing sellers say they won't return. EBay's management isn't speculating on whether the site's changes have alienated a material percentage of its merchants, and representatives say eBay has no plans to alter its planned policy changes, despite the outcry.

"As far as longer-term effects, it's too early to speculate," Mallabo said.

Industry experts such as David Steiner, president of a trade publication for online merchants called AuctionBytes, say that the real evidence of a boycott effect, if there is one, will be clearer later in the week, as last week's listings expire.

"If [eBay's listings total] falls below 12 million we've made a pretty good impact," said Nancy Baughman, an eBay PowerSeller who deals antiques and co-authored Buy It, Sell It, Make Money, a guide to doing business on eBay. "I'm hoping that it goes down below 10 million. If that happens, we will have made a huge impact."

Tomorrow will be a key day for testing eBay's listings strength: a host of fee changes take effect, lowering the insertion fee eBay charges for listing new items but raising the "final value fee" it levies on its that sell. Other controversial aspects of eBay's overhaul, including a change that bars sellers from leaving negative feedback on buyers, are slated for rollout in later months and will not be introduced Wednesday alongside the fee changes.

Some boycotting sellers have already declared victory, despite the debate over whether eBay's listing numbers have been impacted.

"My view on the whole thing is we've already been a success," said Valerie Lennert, a doll-clothing vendor in Anaheim, Calif., who has drawn attention to the strike through a YouTube video she posted three weeks ago. "I'm doing about 10 interviews a day. The goal of the strike is to get eBay's attention and we finally have it. Anything else is icing on the cake."

Protestors also point to one other small victory: Rising listings numbers on rival auction sites.

Carol B., a Kansas City, Mo., antique jewelry seller, is joining the effort to create more competition for eBay. (She asked that her last name not be used in this article.) Like other frustrated sellers, she is planning to move most of her inventory off of eBay and is testing out other auction sites.

"I'm going to try iOffer because it's very inexpensive," said Carol, who makes about $5,000 a month selling sterling silver charms.

Lennert plans to continue to promote about 10% of her merchandise on eBay while building traffic to storefronts she is creating on other sites - including, eventually, her own website.

"I don't think any sellers believe we can crush eBay in a week," Baughman said. "We want eBay to acknowledge that these changes may not be the best for smaller sellers. I want eBay to make money, but can we make some too? I think [eBay] has a moral responsibility not to drive these people out the marketplace, especially considering the state of the economy."

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