The percentages represent the share of physical gross merchandise sales sold on Amazon by independent third- party sellers – mostly small- and medium-sized businesses – as opposed to Amazon retail’s own first party sales. Third-party sales have grown from 3% of the total to 58%.
Our first-party business has grown dramatically over that period, from $1.6 billion in 1999 to $117 billion this past year. The compound annual growth rate for our first-party business in that time period is 25%. But in that same time, third-party sales have grown from $0.1 billion to $160 billion – a compound annual growth rate of 52%.- Jeff Bezos, 2018 Letter to Shareholders
From 56.0% in 2017 it increased by 4% to 58.0% in 2018.
Source: Amazon Quarterly Results.