As anticipated, AT&T said Wednesday it will soon replace its unlimited wireless data plan with a series of metered pricing tiers that charge subscribers according to the number of megabytes they consume on a monthly basis. The new rate schedule will impact new AT&T smart phone subscribers and will go into effect simultaneously with the release of Apple’s upgraded iPhone model. (Current AT&T customers will be able to keep indefinitely their existing data plans that provide unlimited usage for $30 monthly.) AT&T’s move also provides the first evidence of a long expected industry-wide shift toward tiered data pricing as the proliferation of smart phones with sophisticated applications and burgeoning subscribership to wireless data services combine to strain increasingly scarce supplies of bandwidth. (In an interview last month with the Wall Street Journal, Lowell McAdam, the CEO of U.S. market leader Verizon Wireless, acknowledged that his company is also considering usage-based pricing built on “buckets of megabytes” as he predicted that “the old model of one price plan per device is going to fall away.”) Starting Monday, new AT&T smart phone customers will be given their choice of two data plans. The first, priced at $15 per month, will cover a maximum 200 megabytes of data traffic per month, equating to 1000 e-mails without attachments, an additional 150 e-mails with attachments, access to 400 web pages, the ability to upload 50 photos, and up to 20 minutes of streaming video. According to AT&T, 65% of current data customers use less than 200 MBs per month, and customers who exceed that amount will be given the option to purchase an additional 200 MBs for $15. Dubbed “DataPro,” the second plan encompasses 2 gigabytes of data usage at a monthly rate of $25. DataPro subscribers who exceed the 2 GB allotment will be able to purchase additional 1 GB increments at $10 each. New users of the Apple iPad will be required to subscribe to DataPro, which also offers iPad and iPhone customers the option of “tethering” their wireless devices to a personal computer for an additional monthly charge of $20. Anticipating the shift toward greater data usage, AT&T and Verizon announced cuts to the prices of their unlimited voice calling plans early this year. Noting that the new rates will reduce the cost of service for many data customers, AT&T wireless operations chief Ralph de la Vega predicted, “I think what it’s going to do is bring more people into the smart phone marketplace.”