Third-party sellers' share of physical gross merchandise sales on Amazon has grown from 3% of the total to 58%.

TRUE: Amazon's published figures (its shareholder letters, filings or official statements) show that third-party sellers' share of physical gross merchandise sales was about 3% in 1999 and 58% in 2018. MOSTLY TRUE: both endpoints hold within about 2 percentage points, or one endpoint year is off by a year. MOSTLY FALSE: the figures are real but measure something different from the claim, such as units rather than gross merchandise sales, or a different period, so the claim as stated misrepresents them. Mostly false also applies if one endpoint is off by more than a few points. FALSE: the evidence shows that the third-party share in 2018 or in 1999 was materially different, more than 5 points from the claimed figure.

Set before the research began.

1. E1 Here's Jeff Bezos' annual shareholder letter CNBC · 11 April 2019

   “1999 3% 2000 3% 2001 6% 2002 17% 2003 22% 2004 25% 2005 28% 2006 28% 2007 29% 2008 30% 2009 31% 2010 34% 2011 38% 2012 42% 2013 46% 2014 49% 2015 51% 2016 54% 2017 56% 2018 58%”

2. E2 Amazon: Third-Party Sellers are Kicking our First-Party Butt Seattle Business Magazine · 11 April 2019

   “The percentage of merchandise sold by independent third-party sellers on Amazon.com has increased markedly the past 20 years and now represents 58 percent of gross merchandise sales, CEO Jeff Bezos wrote in his annual letter to shareholders.”

3. E3 Amazon: Third-Party Sellers are Kicking our First-Party Butt Seattle Business Magazine · 11 April 2019

   “In 1999, third-party sellers represented just 3 percent of sales, or $1.6 billion.”

CNBC's reproduction of the 2018 shareholder letter [E1] gives a year-by-year series that starts at 3% in 1999 and reaches 58% in 2018. Seattle Business Magazine [E3] reports that the letter puts third-party sellers at 58 percent of gross merchandise sales. The same magazine [E4] says the figure was 3 percent in 1999. Both independent outlets give 3% for 1999 and 58% for 2018 [E1][E3][E4], and E3 identifies the 58 percent figure as a share of gross merchandise sales, so under the criteria the claim resolves true.