Deidra Cheeks Merriwether
Chief Financial Officer, Senior Vice President at W.W. Grainger
Thanks, D.G. Turning to our High-Touch Solutions segment. We continue to see a robust recovery with daily sales up 13.7% compared to the second quarter of 2020 and up 9.5% compared to the second quarter of 2019. In the U.S., we saw strong growth in our non-pandemic product category with product mix returning to more normal levels. For the segment, GP finished the quarter at 36.9%, down 125 basis points versus the prior year.
I think it's important to note that without the $63 million of inventory adjustment, GP would have been up 125 basis points year-over-year. This 250 basis point swing demonstrates that our underlying GP rate would have otherwise been a healthy 39.4%. Coupled with our focus on achieving price/cost neutrality, we are confident that our run rate GP remains strong. SG&A in the segment ramped as expected to $640 million, lapping the lowest point of SG&A spend in the second quarter of 2020. Canada continued to make solid progress and expanded operating margin approximately 315 basis points year-over-year. Consistent with last quarter, we have included a chart with details on the U.S. and the Canadian businesses on the first page of the appendix.
On slide 10, looking at pandemic product trends, I want to highlight two things before we dive into the Q2 numbers. First, we lapped the extreme growth experienced last year and saw decreased demand for PPE products. Accordingly, pandemic sales declined approximately 28% versus 2020. However, that's an impressive 27% increase versus 2019. We estimate July 2021 will be down about 28% over July 2020, in line with what we saw in the second quarter of this year. More importantly, we see the trend in our non-dynamic sales as a positive sign of economic recovery. During the quarter, we grew 31% versus 2020 and up 7% versus 2019. We're seeing end markets like commercial, which include our severely disrupted customers in hospitality, along with heavy manufacturing, make a significant comeback. We estimate that for the month of July 2021, non-pandemic sales growth of about 22%. As it relates to pandemic product mix, while we expected it to taper off to near pre-pandemic levels to about 20% by year-end, we're seeing this happen more quickly now at about 22% of sales.
In total, our U.S. High-Touch Solutions business is up about 12% for the second quarter of 2021 and up 10% over 2019. Looking at market outgrowth on slide 11, we are lapping the highest concentration of large pandemic purchases of the prior year. At this time, the market declined between 14% and 15% and we saw outsized share gains of roughly 1,200 basis points. For Q2 2021, we're seeing the opposite effect. We estimate the U.S. MRO market grew between 18.5% and 19.5%. The U.S. High-Touch business grew 12.4%, about 650 basis points lower than the market. To normalize for the volatility, we calculated the two-year average share gain to be 275 basis points over the market. There's some noise in the market number because -- across industrials, given the dynamics and fluctuations over the last two years. Therefore, the two-year average is a better estimate of what's really going on.
As I previously noted, our U.S. High-Touch business is up 10% over 2019. As the impact of the pandemic subsides, coupled with our strong progress on key initiatives and our return on investments like marketing, we remain confident in our ability to achieve our share gain goals. Now let's cover our U.S. GP rate. As previously discussed, our second quarter GP decline resulted from the $63 million inventory adjustment. This adjustment lowered U.S. GP by 270 basis points. Without this, our underlying U.S. GP rate is 39.8% in the second quarter. As we look to the remainder of 2021, it is important to note we are operating in a very challenging and fluid environment. We're doing everything within our control to exit the year with a Q4 GP rate at or above the Q1 2020 levels or 40.1%. We remain confident in our ability to achieve this target for a few reasons. First, as noted earlier, we anticipate no further material pandemic-related inventory adjustments. Excluding the inventory impacts, our GP rate is nearing this level already.
As we discussed on slide 10, our pandemic product mix is close to pre-pandemic levels, and we expect this to fully normalize in the second half. And we've seen evidence that we can continue to maintain price/cost neutrality. On the cost side, we have a robust process to partner with our suppliers and understand the specific raw material impacts as well as other conditions that may result in increased costs. As it relates to price, our goal is to continue to maintain competitiveness in the market and pass what is applicable. In the first half, we were slightly above neutrality and as we expect to take additional price increases in the second half to offset what we're expecting in costs. Even in this inflationary environment, we are confident we will be able to execute and achieve neutrality through the remainder of the year. Moving to our Endless Assortment segment.
Daily sales increased 23% or 23.9% on a constant currency basis, driven by continued strength in new customer acquisitions at both Zoro and MonotaRO as well as growth of larger enterprise customers in MonotaRO. GP expanded 75 basis points year-over-year driven by positive trends at both businesses, and operating margin finished up 95 basis points over the prior year. I'll go into more detail on the next slide as we provide further transparency on the results of both of these businesses. Moving to slide 14. Please remember that MonotaRO is a public company and follows Japanese GAAP, which differs from U.S. GAAP and is reported in our results one month in arrears. As a result, the numbers we disclose will differ somewhat from MonotaRO's public statements. In local currency and using Japan's local selling days, which occasionally differ from U.S. selling days, MonotaRO's daily sales grew 16.7% with GP finishing the quarter at 26.4%, 25 basis points above the prior year. Operating margin decreased 15 basis points to 12% as they continue to ramp up operations at the Ibaraki DC.
Again, another strong quarter for MonotaRO. Switching to Zoro U.S., daily sales grew 32.6% as it laps its softest quarter of 2020. Zoro GP grew 95 basis points to 31.5% and achieved 320 basis points of operating margin expansion through substantial SG&A leverage in the quarter. All in all, very impressive results. Moving to slide 15. In addition to the strong financial performance, we're seeing positive results with our key operating metrics. As you saw in the first quarter, we've listed total registered users for both businesses, an important driver of top line performance. Both MonotaRO and Zoro have shown progress and are up over 20% over the second quarter last year. On the right, Zoro continues to actively add SKUs to the portfolio. At the end of the second quarter of 2021, we had a total of 7.5 million SKUs available online, close to our goal of eight million for the year. We remain encouraged by our progress with SKU additions beyond traditional MRO. Now I'll provide commentary as it relates to the upcoming quarter and our expectations for the full year.
For the third quarter, on a total company level, we expect our revenue growth to be between 10% and 11% on a daily organic basis. We believe any material pandemic-related inventory adjustments are complete, and we expect GP to be up between 100 and 120 basis points year-over-year and to improve sequentially. SG&A is anticipated to fall between $805 million and $815 million as we continue to invest in marketing and wages in the DCs to remain competitive. Transitioning to our total company guidance, I'd like to provide some brief commentary on how we're trending so far. We expect strong sales to continue while GP, operating margin and EPS will face pressure as a result of the incremental inventory adjustments and freight costs, along with investments and increased DC wages and marketing.
While we are maintaining our guidance, we expect results will trend towards the low end of our range with the exception of revenue. We expect revenue to be near the midpoint. As it relates to our segment operating margins, we think that some of the supply chain challenges as well as the first half inventory adjustment will weigh more heavily on the High-Touch Solutions segment and therefore, High-Touch operating margin may trend at the low end of the range. At the same time, we believe Endless Assortment, driven by strong performance and improving margins, may end the year at the high end, both helping to support delivery of total company results. We are not adjusting guidance as we are confident in our ability to deliver results within our guidance ranges. As we learn more, we'll continue to keep you apprised of any changes.
With that, I'll turn it back over to D.G. for some closing remarks.