According to the wine industry advisor, 

The wine and spirits business continues to evolve, with producers and buyers alike looking for more service, more flexibility, and more choice. Independent Distributor Network (IDN) is a unique model, whose members are local, family-owned distributors working together to offer wine and spirits producers an alternative solution to establish a national footprint, and buyers with a greater choice in selection.

“The top 10 wine and spirits distributors account for roughly 75% of the national market,” says David Stubblefield, President of the IDN Board or Directors. “Distributor consolidation has been a trend for the past 20 years. It has led to more efficiency and economies of scale for those companies, but has also left more niche or craft wine and spirits brands with fewer options for 3-tier sales.”

Read more at source: wine industry advisor