As reported with respect to operating income at $135.9 million, operating income percentage at 6.2% and with respect to earnings per diluted share at $1.76 on a non-GAAP adjusted basis.
We earned revenues of $2.2 billion in the quarter and had operating cash flow of $270 million.
We have structurally reduced our SG&A by about $7 million to $9 million per quarter on a go-forward basis.
We leveraged our cost structure across a solid mix of projects to earn strong and robust operating income margins of 9.2% in our Electrical Construction segment and 9% in our Mechanical Construction segment.
With a record quarterly operating income percentage of 6.9%.
Number 5, we have positioned ourselves into some good long-term markets, which I will talk about later, such as healthcare, manufacturing, high-tech manufacturing, data centers, commercial and food processing.
Consolidated revenues of $2.2 billion are down $86 million or 3.8% from quarter 3, 2019.
Our third quarter results include $81.4 million of revenues attributable to businesses acquired, pertaining to the time that such businesses were not owned by EMCOR in last year's third quarter.
Excluding the impact of businesses acquired, third quarter consolidated revenues decreased approximately $167.5 million or 7.3%.
United States electrical construction revenues of $508.9 million decreased $45.8 million or 8.3% from 2019's third quarter.
United States Mechanical Construction segment revenues of $891.5 million, increased $22.3 million or 2.6% from quarter three of 2019.
The results of this segment represent record third quarter revenue performance, excluding acquisition revenues of $61.1 million, the segment's revenues decreased $38.8 million or 4.5% organically.
EMCOR's total Domestic Construction business third quarter revenues of $1.4 billion decreased by $23.5 million or 1.6%.
United States Building Services quarterly revenues of $551.5 million increased $19.4 million or 3.7% and represents an all-time quarterly record for this segment.
Excluding acquisition revenues of $20.3 million, this segment's revenues decreased approximately $900,000 or less than 0.25%.
United States Industrial Services revenues of $139.7 million decreased $94.4 million or 40.3% and as this segment continues to be impacted by the negative macroeconomic conditions and uncertainty within the markets in which it operates.
United Kingdom Building Services segment revenues of $110.1 million increased $12.5 million or 12.7% from last year's quarter.
In addition, revenues of this segment were positively impacted by $5 million as a result of favorable foreign exchange rate movements within the quarter.
Selling, general and administrative expenses of $226.8 million represent 10.3% of third quarter revenues and reflect an increase of $6.7 million.
The current year's quarter includes approximately $8.9 million of incremental expenses from businesses acquired, inclusive of intangible asset amortization, resulting in an organic quarter-over-quarter decrease in selling, general and administrative expenses of approximately $2.2 million.
SG&A expenses for the third quarter of 2019 and were favorably impacted by $4.5 million of insurance recovery and legal settlements within the Industrial Services segment.
When excluding these recoveries from the prior year period, the adjusted organic decline in 2020's third quarter SG&A is $6.7 million.
Additionally, with quarter-over-quarter a sequential increase in total incentive compensation expense previously mentioned, our SG&A as a percentage of revenues was unfavorably impacted by approximately 50 basis points within the third quarter of 2020.
Reported operating income for the quarter of $135.9 million represents a $20.1 million increase or 17.4% as compared to operating income of $115.7 million in 2019's third quarter.
Our third quarter operating margin is 6.2%, and which favorably compares to the 5.1% of operating margin reported in last year's third quarter.
Specific quarterly performance by reporting segment is as follows: Our U.S. Electrical Construction segment operating income of $47.1 million increased $13.4 million from the comparable 2019 period.
Reported operating margin of 9.2% represents a 310 basis point improvement over last year's third quarter.
In addition, operating income and operating margin of this segment benefited from favorable project closeouts within the transportation and institutional market sectors, which positively impacted quarterly operating margin in the current year by 70 basis points.
Third quarter operating income of our U.S. Mechanical Construction Services segment of $80 million represents an $18.8 million increase from last year's quarter, while operating margin in the quarter of 9% and represents a 200 basis point improvement over 2019.
Our combined U.S. construction business is reporting a 9.1% operating margin and $127.1 million of operating income, which has increased from 2019's third quarter by $32.3 million or 34%.
For the third quarter of 2020, operating income and operating margin for our U.S. Building Services segment was $38.2 million and 6.9%, respectfully.
Operating income increased by $3.2 million over last year's third quarter, and operating margin improved by 30 basis points.
Our U.S. industrial services operating loss of $9.8 million represents a decrease of $15.4 million compared to operating income of $5.6 million in last year's third quarter.
U.K. Building Services operating income of $5.3 million represents an approximately $600,000 increase over 2019's third quarter due to an increase in gross profit within the segment.
Operating margin of 4.8% is slightly reduced from 2019's third quarter operating margin of 4.9%.
And additional financial items of significance for the quarter not addressed on my previous slides are as follows: quarter three gross profit of $363.2 million or 16.5% of revenues is improved over last year's quarter by $27.2 million and 180 basis points of gross margin.
Diluted earnings per common share of $1.11 and compares to $1.45 per diluted share in last year's third quarter.
Adjusting our record quarterly performance for the negative impact on our income tax rate resulting from the nondeductible portion of the noncash impairment charges recorded during the second quarter of this year, non-GAAP diluted earnings per share for the quarter ended September 30, 2020, and is $1.76, which favorably compares to last year's quarter by $0.31 or 21.4%.
My last comment on this slide is a continuation of my income tax rate commentary which, as you can see on the bottom of slide nine, is 54.7% for the quarter due to the nondeductibility of the majority of quarter two's noncash impairment charges.
With one quarter of 2020 remaining, I anticipate that our full year tax rate will be between 53% and 54%, which is a downward revision from the previous range provided on our quarter two call.
Revenues of $6.52 billion, representing a decrease of $255.1 million or 3.8% and when compared to revenues of $6.77 billion in the corresponding prior year period.
Our year-to-date results include $214.1 million of revenues attributable to businesses acquired, pertaining to the period of time that such businesses were not owned by EMCOR in the 2019 year-to-date period.
Excluding the impact of businesses acquired, year-to-date revenues decreased organically 6.9%, primarily as a result of the significant revenue contraction experienced during quarter 2, given the containment and mitigation measures mandated by certain of our customers as well as numerous governmental authorities in response to COVID-19.
Year-to-date gross profit of $1 billion is higher than the 2019 nine month period by $20.4 million or 2.1%.
Year-to-date gross margin is 15.5% and which favorably compares to 2019's year-to-date gross margin of 14.6%.
Selling, general and administrative expenses of $659 million represent 10.1% of revenues as compared to $652.5 million or 9.6% of revenues in the prior year period.
Year-to-date 2020 includes $25.2 million of incremental SG&A, inclusive of intangible asset amortization pertaining to businesses acquired.
Excluding such incremental cost, our SG&A has decreased on an organic basis, by approximately $18.7 million year-over-year.
Reported operating income for the first nine months of 2020 is $119.2 million, adjusting this amount to exclude the noncash impairment loss on goodwill, identifiable intangible assets and other long-lived assets recorded in the second quarter, results in non-GAAP operating income of $352 million for 2020's nine month period as compared to $338 million for the corresponding 2019 year-to-date period.
This adjusted non-GAAP operating income represents a $13.9 million or 4.1% improvement year-over-year.
Diluted earnings per common share for the nine months ended September 30, 2020, is $0.96 when adjusting this amount for the impact of the noncash impairment charges previously mentioned, non-GAAP diluted earnings per share was $4.54, and as compared to $4.22 in last year's nine month period.
This represents a $0.32 or 7.6% improvement period-over-period.
EMCOR's liquidity profile continues to improve as we just completed another quarter of strong cash flow generation, bringing our year-to-date operating cash flow to $546.8 million.
On a year-to-date basis, these measures have favorably impacted operating cash flow by approximately $81 million.
With this strong operating cash flow, cash on hand has increased to $679.3 million, from the approximately $359 million on our year-end 2019 balance sheet and is the primary driver of the increase in our September 30 working capital balance.
Largely as a result of $44.8 million of amortization expense recorded during the first nine months of this year.
Total debt has decreased by approximately $30 million since the end of 2019, reflecting our net financing activity during the year.
Although not included on this slide due to the periods presented, EMCOR has paid down approximately $273 million of borrowings under its credit facility, inclusive of borrowings executed during 2020.
And EMCOR's debt to capitalization ratio has decreased to 12.3% as of September 30.
Total RPOs at the end of the third quarter were a little over $4.5 billion, up $495 million or 12.3% when compared to the September 2019 level of $4 billion.
RPOs, likewise, increased the same amount, $494 million for the first nine months of 2020.
With all this growth being organic, except for approximately $86 million relating to two acquisitions in the current 12-month period.
Taken together, our Mechanical and Electrical Construction segment, RPOs have increased $409 million or 12.4% since the year ago period.
Commercial project RPOs comprised our largest market sector at over 42% of total.
This is almost a 20% increase from the year-end, and it's really spurred by two things: really high-tech and data center projects it bears repeating.
So I'm going to take the next two pages and cover on pages 13 and 14.
And I'm now going to turn to page 13, and it says future affects our markets.
We've done a good job here, and we're one of the leaders, and we've also made some strategic acquisitions, especially in the last 15 months, not only in fire protection assets, but also key electrical contractors like we did in the Midwest and also in the Southeast, which is emblematic of our BKI acquisition.
So facilities are going to have to move between the 2.
As we switch to page 14.
Really the goal over the last 20 years.
And actually, buildings are going back to 25 CFM per person, and that's cubic feet per minute.
And we had got that down to 15%.
We take things from a Merck 10 or 12 up to a 14 or 15.
Needle 0.5 polar ionization, we're one of the leaders in the implementation of that technology.
This is someone that has 240 buildings.
We'll do this across 240.
We'll do this in 90 sites.
That retro market is going to gain strength as we move through 2021 on the HVAC side.
With that, I'm going to turn to the last two pages, 15 and 16, and I'm going to close out here.
We will move to $5.90 to $6.10 non-GAAP adjusted earnings per share and revenues of around $8.7 billion.
And if you refer back to page 13, we have a lot of operating space in what we believe are resilient markets.

Summary:
As reported with respect to operating income at $135.9 million, operating income percentage at 6.2% and with respect to earnings per diluted share at $1.76 on a non-GAAP adjusted basis.
We earned revenues of $2.2 billion in the quarter and had operating cash flow of $270 million.
Diluted earnings per common share of $1.11 and compares to $1.45 per diluted share in last year's third quarter.
Adjusting our record quarterly performance for the negative impact on our income tax rate resulting from the nondeductible portion of the noncash impairment charges recorded during the second quarter of this year, non-GAAP diluted earnings per share for the quarter ended September 30, 2020, and is $1.76, which favorably compares to last year's quarter by $0.31 or 21.4%.
That retro market is going to gain strength as we move through 2021 on the HVAC side.
We will move to $5.90 to $6.10 non-GAAP adjusted earnings per share and revenues of around $8.7 billion.