Amazon said in January that it was considering increasing the annual subscription rate on its Amazon Prime program — which includes free two-day shipping on many purchases and access to the site’s library of streaming videos — by twenty to forty dollars. This morning, the e-tailer began notifying customers that it is indeed jacking up that rate from $79/year to $99/year.

Reads the e-mail being sent to Prime members:

We are writing to provide you advance notice that the price of your Prime membership will be increasing. The annual rate will be $99 when your membership renews… Even as fuel and transportation costs have increased, the price of Prime has remained the same for nine years. Since 2005, the number of items eligible for unlimited free Two-Day Shipping has grown from one million to over 20 million. We also added unlimited access to over 40,000 movies and TV episodes with Prime Instant Video and a selection of over 500,000 books to borrow from the Kindle Owners’ Lending Library.

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UPDATE: Readers with Amazon Student Prime accounts say their yearly rates are also increasing by $10 to $49/year.

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UPDATE #2: Because of discrepancies between renewal dates mentioned in e-mails sent to Prime subscribers and what some members were seeing on their account profiles, Consumerist spoke to Amazon, which confirmed that new users will be able to sign up for Prime at the current $79 rate until March 20. Existing members whose accounts renew before April 17 will have their memberships re-upped at the current rate. Any memberships purchased after March 20 or renewed after April 17 will be at the $99 rate.

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Some consumers have reacted negatively to speculation that the annual rate could increase so dramatically at once. As we’ve argued in the past, Amazon would be facing less of a backlash if it charged a monthly rate, as the prospect of going from $6.58/month ($79/year) to $8.25/month ($99/year) may not have seemed as drastic to some consumers.

What remains to be seen is whether those angry customers will ditch their Prime subscriptions when it comes time to renew.