Amazon upped its free shipping minimum by $10 to $35 on Tuesday, marking the first time in a decade that the company has increased that threshold.

In its announcement for the increase, Amazon pointed out that "during that time, we have expanded free shipping selection by millions of items across all 40 product categories."

This sort-of stealth increase is one way Amazon can help deliver the kind of bottom-line results that investors are seeking. The company has blithely ignored such cries for years, though, instead focusing on growth and pleasing consumers.

However, as the New York Times points out, Amazon also quietly overhauled its next-day shipping fee for Prime customers over the summer. Previously, customers who paid a $79 annual fee to join Prime paid just $3.99 to have such items shipped, regardless of size. Now, the company takes size and weight into account and charges accordingly.

Rather than penny-pinching, though, the increase might also be a subtle way to herd more customers over to Prime. Amazon's announcement included a plug for that service.

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