Here's another key finding from the soon-to-be-released 2016 ProSales 100: The top 10 firms on the list account for 69.1% of the entire group's sales last year. That's an increase of almost eight percentage points from the 2015 report and the biggest share since we compiled the figures as far back as 2002.

As we reported April 20, the nation's biggest pro-oriented construction supply companies sold a collective $41.74 billion worth of goods last year. Of that total--the biggest, by the way, since 2006, when the housing boom was cresting--the first- through 10th-place dealers on the 2016 list accounted for $28.84 billion of those sales.

This swell in the top 10's dominance is largely the result of three megamergers that took place last year, in which Builders FirstSource (No. 6 on the 2015 ProSales 100 list) acquired No. 2 ProBuild, No. 3 Beacon Roofing Supply swallowed up No. 12 Roofing Supply Group, and No. 9 BMC took in No. 10 Stock Building Supply. No. 1 ABC Supply and No. 7 US LBM also made a slew of acquisitions and expansions in 2015. We'll reveal in early May where those companies and the rest of the PS100 stand as a result of the deals.

Likewise, the top 10's share of all facilities also jumped in 2015 to account for 65.0% of the entire ProSales 100's yards. That's up from 56.6% the year before.