Costco has two secret weapons: Kirkland, and a growing number of "home-lennials"

Return of the samples... Nothing sweeter than a free Lindt chocolate. While Amazon Prime Day(s) are in full swing, Costco is still winning over hearts and shopping carts with its old-school approach. Online sales make up only 6% of Costco's total, because shoppers dig the in-store "treasure hunt" (come for the TP, leave with a foldable grill). Now, the Disneyland of bulk retail is increasingly appealing to Millennials — especially first-time home buyers:

• 2M+ Americans bought homes for the first time last year. Nearly 40% of those were Millennials, the most of any generation.
• Costco is catering to Millennial homebuyers with a fresh offering of "healthy" options to stock their starter houses. Think: almond flour and organic applesauce for Baby #1.

Signature rosé... for the Millennial mom. Costco has a secret weapon that other food retailers envy: Kirkland. The private-label offers everything from vodka, to eggs, batteries, and toilet paper. Most Kirkland products are made by third parties. Read: shoppers can sneakily get brand names at off-brand prices. Kirkland coffee = Starbucks, Kirkland diapers = Huggies, Kirkland cran juice = Ocean Spray.

• Bigger than Coke: Kirkland did $52B in sales last year — nearly $20B more than Coca-Cola, and double Kraft-Heinz's annual sales.
• Bigger than cable: Costco memberships now exceed cable TV subscriptions in the US. Kirkland is a key driver of that success.