We made solid improvement in stabilizing one of the key metrics on the Wireless side, postpaid churn. While it was up a modest 3 basis points year-over-year, this is by far the smallest year-over-year increase we've seen in nearly 2 years and as a sequential improvement, a significant one from Q4 as well.
It was also the third straight quarter in which we've been able the slow the year-over-year rate of decline of postpaid voice ARPU, which is another key metric for us on the Wireless side. It's still obviously under pressure in the face of intense competition in the Wireless market, but we have continued to focus on managing this decline as much as possible, given the environment. While the strength of Wireless data offset much of this pressure, we still saw an overall 4% decline in postpaid ARPU.
We're also continuing to drive our wireless data strategy. Despite what was an intensely competitive environment in Q1, we activated over 640,000 smartphones, the second highest number of smartphones ever in a single quarter and the highest during the first quarter. Embedded in that and one of the drivers of expense growth in the quarter was that iPhone activations, including upgrades, were up a full 35% from Q1 of last year. This in part reflects residual demand from Q4 and last year where we are supply constrained for a good portion of the quarter.
With continued solid success in the high-value smartphone category, and we now have 60% of our postpaid subscriber base on smartphones. The smartphone metrics, ARPU, churn and upgrade rate remain healthy given the competitive backlog. And at the same time, we're both attracting and retaining our highest lifetime value customers, which is squarely on our strategy. As a result, we continue to drive double-digit revenue growth in our Wireless Data business, which is the most significant driver of our top line.Read the rest of this transcript for free on seekingalpha.com