The combination of “rational” competition and shortages in the supply of Apple’s new iPhone X will conspire to significantly reduce the expected growth in wireless customer additions in the fourth quarter, according to a new report from Wall Street investment firm Jefferies.

Specifically, the firm said it lowered its estimates for wireless carriers’ customer net handset additions by an overall 23% for the fourth quarter. That breaks down to:

Verizon: 685,000 postpaid customer additions in Q4, down from a previous estimate of 808,000.

AT&T: 445,000 postpaid customer additions in Q4, down from a previous estimate of 568,000.

T-Mobile: 1,060,000 postpaid customer additions in Q4, down from a previous estimate of 1,115,000.

Sprint: 200,000 postpaid customer additions in Q4, down from a previous estimate of 365,000.

“As a result, industry service margins move higher by nearly 40bps,” the Jefferies analysts wrote in their report. “In our view, TMUS remains best positioned fundamentally heading into 2018, though tax reform benefits T and VZ the most, but is not yet embedded in estimates.”

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On T-Mobile specifically, the analysts said the operator remains positioned to beat Wall Street expectations on net adds or EBITDA—or both: “While the more benign competitive environment could suppress some volume for T-Mobile, we believe seasonal industry churn is a benefit driving improved porting in the quarter.”

Jefferies’ estimates largely dovetail with holiday sales checks from the likes of Wave7 Research. “Some investors worried that with the T-Mobile/Sprint deal off, competition would return to the intense levels seen in 2016. This has not materialized, with no service pricing cuts, no crazy iPhone offers, and the end of Verizon’s $650 ETF (early termination fee) buyout,” Wave7 wrote in a note to subscribers in December. “AT&T does have a multi-OEM BOGO that includes iPhones, but T-Mobile has no iPhone offers at all and Sprint has weakened its iPhone offer. Verizon’s offer is modest, as it requires trade-in of a valuable phone to get a $300 credit.”

Similarly, the analysts at Wall Street research firm Barclays wrote in December that “Commentary by AT&T, Verizon and Sprint all reiterated that the competitive landscape remains subdued with just three weeks of the holiday promotional season remaining. However, our view, promotional activity is likely to remain relatively rational given several dynamics.”

While the nation’s top wireless carriers may not have been as aggressive during the fourth quarter with customer acquisition efforts as in previous years, investors may well cheer that action in the hopes it will result in improved financials and customer metrics.