Data Center Transformer Market Size, Share & Forecast to 2035

The Data Center Transformer Market covers the transformers bought to power data centers: large power transformers in campus and delivery substations, medium-voltage distribution transformers that step grid power down to building voltage, low-voltage dry-type transformers inside power distribution units and plant rooms, and the first solid-state transformers built for direct current power systems. DC Market Insights values the global Data Center Transformer Market at USD 3.48 billion in 2025 and forecasts USD 8.18 billion by 2035, a CAGR of 8.93%. The 2025 value is built from the capacity itself: about 13.4 GW of IT capacity energized or prepared for energization (45% of 2025 completions of 12.0 GW plus 55% of 2026 completions of 14.5 GW, because transformers are delivered ahead of the IT load) at about USD 0.25 million of new-build transformer spend per MW of IT load gives USD 3.29 billion, and replacement and upgrade work on an installed base of about 104 GW adds USD 187.88 million. Solid-state transformers are the fastest-growing segment at 42.44% a year because DC Market Insights expects 800-volt direct current (VDC) power systems for AI racks to use power electronics in place of conventional transformers, and the Middle East and Africa is the fastest-growing region at 12.65% a year in the DC Market Insights model as the region adds campus-scale capacity from a small installed base.

Executive Summary

The Global Data Center Transformer Market size was valued at USD 0.98 billion in 2020, reached USD 3.48 billion in 2025, and is anticipated to reach USD 8.18 billion by 2035, at a CAGR of 8.93% during the forecast period.

Report attribute	Details
Historical Period	2020-2024
Base Year	2025
Forecast Period	2026-2035
Data Center Transformer Market Size 2025	USD 3.48 Billion
Data Center Transformer Market, CAGR	8.93%
Data Center Transformer Market Size 2035	USD 8.18 Billion

The market grew at 28.93% a year between 2020 and 2025, and 2025 alone added 26.4% over 2024. Two forces stacked on top of each other: annual capacity completions more than doubled from 5.0 GW in 2020 to 12.0 GW in 2025 in the DC Market Insights capacity model, and the price of a medium-voltage transformer rose from about USD 30.5 thousand per megavolt-ampere (MVA) in 2020 to USD 53.6 thousand per MVA in 2025 while Wood Mackenzie reported transformer supply deficits.

Growth slows to 8.93% a year from 2025 to 2035 because transformer prices flatten once new factories in the United States and Asia reach output, while annual completions keep rising to 22.0 GW in 2030 and 27.0 GW in 2035. The installed base grows from about 116 GW at the end of 2025 to about 318 GW by 2035, which lifts replacement and upgrade spending from 5.4% of the market to 10.7%.

Market Scope: What Does the Data Center Transformer Market Cover?

The Data Center Transformer Market covers every transformer bought for a data center, from the grid connection to the rack, valued at first sale in current US dollars, with 2025 as the base year and forecasts to 2035. DC Market Insights sizes it at USD 3.48 billion in 2025.

Included. Power transformers above 10 MVA in substations that serve a data center, medium-voltage distribution transformers (liquid-filled pad-mount units and cast-resin or vacuum-pressure-impregnated (VPI) dry-type units), low-voltage dry-type transformers in power distribution units and plant rooms, solid-state transformers, and replacement and upgrade units on operating sites.

Excluded. Switchgear, protection relays, civil works and installation labor, uninterruptible power supplies (UPS), busways, instrument transformers, generator step-up transformers at power plants, and grid transformers not dedicated to a data center.

How the segments fit together. The type, technology, power rating, data center type and project type splits each re-cut the same USD 3.48 billion. Power transformers in this report equal the transformer line of the Data Center Substation Market report, which values them at USD 2.02 billion in 2025, so the two models can be read side by side. Solid-state transformers appear both as a type and as a technology.

Market Drivers: What Drives the Data Center Transformer Market?

Three drivers explain most of the growth in the Data Center Transformer Market: a construction pipeline worth about USD 5.69 billion of transformers, electricity demand that the International Energy Agency (IEA) expects to more than double by 2030, and long-term supply agreements.

More Than 23 GW Under Construction Carries About USD 5.69 Billion of Transformers

BloombergNEF counted 23.1 GW of data center capacity under construction globally at the end of September 2025, split across 831 sites, with the United States hosting 15.9 GW of it. At the DC Market Insights estimate of USD 0.25 million of new-build transformer spend per MW of IT load, that pipeline alone carries about USD 5.69 billion of transformers, more than one and a half years of 2025 market value. DC Market Insights sizes medium-voltage transformer capacity at about 1.6 MVA per MW of IT load, in line with a Schneider Electric reference design for a site scalable to 56.16 MW that uses 36 medium-voltage (12 kV to 400 V) transformers rated 2,500 kVA each, or 90 MVA in total.

Data Center Electricity Use Rises from 415 TWh to About 945 TWh by 2030

The IEA estimates that data centers used 415 terawatt-hours (TWh) in 2024, about 1.5% of world electricity consumption, and expects their consumption to more than double to around 945 TWh by 2030. The United States accounted for 45% of data center electricity consumption in 2024.

Big Tech Buyers Lock In Power Equipment Supply Through 2028

Big tech buyers now sign multi-year supply agreements. In September 2026, Hyosung Heavy Industries signed ultra-high-voltage transformer supply contracts totaling KRW 386.5 billion (about USD 286 million) with two US big tech companies, for 765 kV and 345 kV transformers that will be deployed in new AI data centers in the northern and southern United States. In July 2026, HD Hyundai Electric signed a long-term framework agreement worth up to KRW 1.12 trillion (about USD 720 million) with a global big tech company for distribution and high-voltage equipment for data centers under construction across North America through 2028.

Market Trends: How Is Data Center Power Conversion Changing?

Data center power conversion is moving toward solid-state transformers, larger units and ester insulating fluids; together, solid-state and ester-fluid transformers rise from 7.1% of the market in 2025 to 18.9% by 2035.

800 VDC Power Opens the Door to Solid-State Transformers

NVIDIA is leading a move to 800 VDC data center power to support 1 MW IT racks, with full-scale production of 800 VDC data centers planned to coincide with its Kyber rack-scale systems in 2027. Its design converts 13.8 kV alternating current (AC) grid power directly to 800 VDC at the data center perimeter and points to solid-state transformer (SST) approaches to enable that transition, with Eaton, Schneider Electric and Vertiv among its data center power system partners. In February 2026, DG Matrix raised a USD 60 million Series A led by Engine Ventures for its multi-port solid-state transformer. DC Market Insights forecasts solid-state transformers to grow from USD 12.37 million in 2025 to USD 425.25 million by 2035, taking 9.0% of new medium-voltage transformer capacity by 2035.

Units Above 100 MVA Grow at 11.46% a Year

In the DC Market Insights model, the largest AI campuses connect at transmission voltage and use fewer, larger transformers. DC Market Insights estimates transformers above 100 MVA at USD 929.31 million in 2025 and forecasts USD 2.75 billion by 2035, which lifts their share from 26.7% to 33.6%.

Ester Fluids Replace Mineral Oil Close to Buildings

Ester fluid-immersed transformers are the fastest-growing liquid-filled technology at 16.95% a year in the DC Market Insights model, from USD 233.79 million in 2025 to USD 1.12 billion by 2035. DC Market Insights expects operators placing medium-voltage transformers closer to data halls to specify ester fluids more often to ease permitting and spacing on dense campuses.

Market Challenges: What Holds the Data Center Transformer Market Back?

Lead times that reached 120 weeks on average in 2024 and prices about 80% above pre-pandemic levels are the two constraints that DC Market Insights expects to cap the pace of the Data Center Transformer Market through 2027.

Transformer Lead Times Reached 120 Weeks

A June 2024 draft report for the US National Infrastructure Advisory Council (NIAC) put transformer lead times at around 50 weeks in 2021 and 120 weeks on average in 2024, and lead times for large substation power and generator step-up transformers at 80 to 210 weeks. The IEA found that wait times for critical grid components such as transformers and cables have doubled in the past three years. Wood Mackenzie expected US supply shortages of 30% for power transformers and 10% for distribution transformers in 2025.

Prices Are About 80% Higher Than Before the Pandemic

The same NIAC draft report found transformer prices 80% higher than at the beginning of the pandemic. DC Market Insights models the price of a medium-voltage transformer at USD 53.6 thousand per MVA in 2025, up 76% from USD 30.5 thousand per MVA in 2020, and expects prices to peak at about USD 56.4 thousand per MVA in 2028 before easing as new capacity arrives.

Efficiency Standards Tighten from 2029

The US Department of Energy (DOE) final rule on energy conservation standards for distribution transformers covers liquid-immersed, low-voltage dry-type and medium-voltage dry-type distribution transformers, with compliance required on and after April 23, 2029 (Source: Federal Register, DOE final rule). DOE projects national energy savings of 4.58 quads full fuel cycle. DC Market Insights expects the rule to support distribution transformer prices from 2029 even as supply loosens.

Market Opportunities: Where Are the New Revenue Pools?

The two largest new revenue pools in the Data Center Transformer Market are AI and GPU cloud campuses, growing at 15.12% a year, and replacement and upgrade work on operating sites, growing at 16.69% a year.

AI and GPU Cloud Campuses Grow to USD 2.21 Billion by 2035

Specialist AI and GPU cloud operators spent USD 539.80 million on transformers in 2025, and DC Market Insights expects their spend to reach USD 2.21 billion by 2035, about four times the 2025 level. Grid-scale direct current is the longer-term option for the largest sites, covered in the Data Center High-Voltage Direct Current (HVDC) Market report.

Replacement and Upgrade Work Reaches USD 879.15 Million by 2035

In the DC Market Insights model, older halls refitted for AI racks need more transformer capacity, and the installed base nearly triples by 2035. DC Market Insights models replacement and upgrade spending at USD 187.88 million in 2025 and USD 879.15 million by 2035.

Pricing: How Much Do Data Centers Spend on Transformers per MW?

A new data center spends about USD 0.25 million on transformers per MW of IT load in 2025, of which about USD 0.14 million per MW goes to substation power transformers. These are DC Market Insights estimates at first sale.

Transformer cost metric	2020	2025	2030	2035
New-build transformer spend per MW of IT (USD million)	0.17	0.25	0.26	0.27
Power transformers per MW of IT (USD million)	0.10	0.14	0.16	0.16
Medium-voltage transformer price (USD thousand per MVA)	30.5	53.6	55.9	54.3
Medium-voltage capacity per MW of IT (MVA)	1.62	1.60	1.58	1.55
Solid-state share of new medium-voltage capacity	0%	0%	3.3%	9.0%

A public price list gives a check on the medium-voltage figure. Supplier Giga Energy puts distribution transformers at roughly USD 40,000 to over USD 150,000, depending on size and voltage, and substation transformers at USD 150,000 to well over USD 2,000,000. At the model price, a 2,500 kVA unit costs about USD 134 thousand, inside that distribution transformer range.

Standards and Regulation: Which Rules Shape Data Center Transformers?

Four sets of rules shape data center transformers: IEEE C57.12.00 for liquid-immersed units, IEC 60076-11 for dry-type units, US efficiency standards and EU ecodesign rules.

IEEE C57.12.00-2021. The Institute of Electrical and Electronics Engineers (IEEE) Standard for General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers sets electrical and mechanical requirements for liquid-immersed distribution and power transformers with 601 V or more in the highest-voltage winding.

IEC 60076-11:2018. The International Electrotechnical Commission (IEC) standard for dry-type transformers covers units with a highest voltage for equipment up to and including 72.5 kV.

DOE distribution transformer standards. The April 2024 final rule took effect on July 8, 2024, and requires compliance on and after April 23, 2029, for liquid-immersed, low-voltage dry-type and medium-voltage dry-type distribution transformers.

EU ecodesign. Commission Regulation (EU) 2019/1783 amends Regulation (EU) No 548/2014, the ecodesign rules for small, medium and large power transformers in the European Union.

Market Segmentation: Which Segment Leads the Data Center Transformer Market?

Power transformers lead the Data Center Transformer Market with 58.0% of 2025 value, hyperscale data centers lead buyers with 46.9%, and mineral oil-immersed units lead technologies with 69.3%. Solid-state transformers are the fastest-growing segment at 42.44% a year, from USD 12.37 million in 2025 to USD 425.25 million by 2035, because DC Market Insights expects 800 VDC power systems for AI racks to replace part of the conventional transformer chain with power electronics.

By Type: Power Transformers Lead with 58.0%

Type	2025 (USD billion)	Share 2025	2035 (USD billion)	CAGR 2025-2035
Power Transformers	2.02	58.0%	5.00	9.49%
Medium-Voltage Distribution Transformers	1.20	34.6%	2.34	6.87%
Low-Voltage Dry-Type Transformers	0.25	7.0%	0.42	5.54%
Solid-State Transformers	0.01	0.4%	0.43	42.44%

Low-voltage dry-type transformers grow slowest because, in the DC Market Insights model, higher distribution voltages inside the hall remove transformation steps at the rack. Figures in the tables may not add exactly because of rounding.

By Technology: Mineral Oil-Immersed Units Lead with 69.3%

Technology	2025 (USD billion)	Share 2025	2035 (USD billion)	CAGR 2025-2035
Mineral Oil-Immersed	2.41	69.3%	5.19	7.97%
Ester Fluid-Immersed	0.23	6.7%	1.12	16.95%
Dry-Type (Cast Resin and VPI)	0.82	23.6%	1.45	5.83%
Solid-State	0.01	0.4%	0.43	42.44%

Dry-type units hold almost a quarter of value because, in the DC Market Insights model, most transformers installed inside data center buildings are cast-resin units. The National Renewable Energy Laboratory (NREL) expects dry-type three-phase transformers to see demand from data centers.

By Power Rating: Units Up to 2.5 MVA Lead with 34.4%

Power rating	2025 (USD billion)	Share 2025	2035 (USD billion)	CAGR 2025-2035
Up to 2.5 MVA	1.20	34.4%	2.37	7.06%
Above 2.5 MVA to 10 MVA	0.26	7.6%	0.82	11.95%
Above 10 MVA to 100 MVA	1.09	31.3%	2.25	7.51%
Above 100 MVA	0.93	26.7%	2.75	11.46%

By Data Center Type: Hyperscale Data Centers Lead with 46.9%

Data center type	2025 (USD billion)	Share 2025	2035 (USD billion)	CAGR 2025-2035
Hyperscale Data Centers	1.63	46.9%	3.68	8.45%
Colocation Data Centers	0.95	27.2%	1.82	6.73%
AI and GPU Cloud Data Centers	0.54	15.5%	2.21	15.12%
Enterprise and Edge Data Centers	0.36	10.3%	0.48	3.01%

AI and GPU cloud data centers overtake colocation before 2035 and reach 27.0% of the market.

By Project Type: New Build Leads with 94.6%

New-build transformers are worth USD 3.29 billion (94.6%) in 2025 and USD 7.31 billion by 2035, growing at 8.30% a year. Replacement and upgrade projects are worth USD 187.88 million (5.4%) and grow at 16.69% a year to USD 879.15 million.

DC Exclusive: The Transformer Spend per MW Model and Type × Buyer Matrix

At USD 1.02 billion in 2025, power transformers for hyperscale campuses are the single largest cell of the matrix and 29.3% of all data center transformer spending. The matrix is a DC Market Insights model, not a shipment count, built from 52 inputs: 32 capacity cohorts (16 years of new-build and installed-base capacity from 2020 to 2035), 4 transformer cost curves, 3 sizing ratios (medium-voltage and low-voltage MVA per MW and solid-state adoption), 4 buyer splits, 5 regional splits and 4 public disclosures used as cross-checks.

2025, USD billion	Power	MV Distribution	LV Dry-Type	Solid-State	Total
Hyperscale Data Centers	1.02	0.52	0.09	0.01	1.63
Colocation Data Centers	0.51	0.36	0.08	<0.01	0.95
AI and GPU Cloud Data Centers	0.33	0.17	0.03	0.01	0.54
Enterprise and Edge Data Centers	0.16	0.15	0.05	<0.01	0.36
Total	2.02	1.20	0.25	0.01	3.48

Hyperscale buyers spend 62.5% of their transformer budget on substation power transformers, against 44.4% for enterprise and edge sites, because they connect at transmission voltage. Enterprise and edge sites spend 13.6% on low-voltage dry-type units, more than twice the hyperscale share of 5.6% in the DC Market Insights model. AI and GPU cloud operators carry the highest solid-state share at 1.1% of their spend.

The transformer spend per MW model behind these figures has two inputs that any reader can check: IT capacity completed each year (12.0 GW in 2025 and 14.5 GW in 2026) and the new-build transformer spend per MW of IT load (USD 0.25 million in 2025). The model and its assumptions are explained on our research methodology page.

Regional Insights: Which Region Leads the Data Center Transformer Market?

North America leads the Data Center Transformer Market with 46.8% of 2025 value, and the Middle East and Africa is the fastest-growing region at 12.65% a year, because, in the DC Market Insights model, the region is adding campus-scale capacity from a small installed base.

North America Leads with 46.8% Share

North American data centers spent USD 1.63 billion on transformers in 2025, and the region is forecast to reach USD 3.40 billion by 2035, a CAGR of 7.63%. The United States hosted 15.9 GW of the 23.1 GW under construction worldwide at the end of September 2025. Hitachi Energy and Eaton are both expanding US transformer manufacturing capacity.

Asia Pacific Holds 26.1% Share

Asia Pacific is worth USD 908.39 million in 2025 and USD 2.42 billion by 2035, a CAGR of 10.31%. BloombergNEF counted 3.2 GW under construction in Asia Pacific across 283 sites at the end of September 2025. In the DC Market Insights model, India, Malaysia and Japan add the most new transformer demand outside China, and Asia Pacific gains 3.5 points of share by 2035, the largest gain of any region.

Europe Holds 17.4% Share

Europe is worth USD 605.59 million in 2025 and USD 1.33 billion by 2035, a CAGR of 8.22%. Europe grows below the global rate in the DC Market Insights model, and transformers placed on the EU market must meet the ecodesign requirements of Regulation (EU) No 548/2014, as amended in 2019, unless exempt.

Latin America Holds 4.7% Share

Latin America is worth USD 163.58 million in 2025 and USD 458.33 million by 2035, a CAGR of 10.85%, led in the DC Market Insights model by Brazil at USD 71.98 million.

Middle East and Africa Holds 5.0% Share

The Middle East and Africa is worth USD 174.02 million in 2025 and USD 572.91 million by 2035, the fastest growth of any region at 12.65% a year. Saudi Arabia is the largest country market in the region at USD 47.86 million in 2025 in the DC Market Insights model, growing at 13.83% a year.

Country Analysis: Which Countries Spend the Most on Data Center Transformers?

The United States is the largest country market for data center transformers at USD 1.49 billion in 2025, 42.9% of global value, followed by China at USD 340.65 million (9.8%) and Canada at USD 136.82 million (3.9%). The 12 largest countries account for 80.1% of 2025 spending.

Rank	Country	Region	2025 (USD billion)	Share 2025	2035 (USD billion)	CAGR 2025-2035
1	United States	North America	1.49	42.9%	3.04	7.36%
2	China	Asia Pacific	0.34	9.8%	0.78	8.57%
3	Canada	North America	0.14	3.9%	0.36	10.16%
4	Germany	Europe	0.13	3.7%	0.27	7.65%
5	Japan	Asia Pacific	0.13	3.7%	0.31	9.00%
6	United Kingdom	Europe	0.12	3.5%	0.25	7.61%
7	India	Asia Pacific	0.10	2.8%	0.39	15.09%
8	Australia	Asia Pacific	0.08	2.4%	0.23	10.67%
9	Brazil	Latin America	0.07	2.1%	0.19	10.47%
10	France	Europe	0.07	2.0%	0.16	8.49%
11	Malaysia	Asia Pacific	0.07	1.9%	0.20	11.58%
12	Saudi Arabia	Middle East and Africa	0.05	1.4%	0.17	13.83%

India is the fastest-growing large country market at 15.09% a year, ahead of Saudi Arabia at 13.83%. The United States grows slowest of the 12, at 7.36% a year. The country figures are a DC Market Insights allocation of the regional totals, weighted by each country’s estimated share of installed and new data center capacity.

Forecast Scenarios: How Could the 2035 Forecast Change?

The Data Center Transformer Market reaches USD 8.18 billion by 2035 in the base case, with a range of USD 6.95 billion to USD 9.21 billion across the low and high scenarios.

Scenario	Assumption from 2026	2035 (USD billion)	CAGR 2025-2035
Low	Capacity additions 15% below base; solid-state adoption 30% slower	6.95	7.16%
Base	Additions rise to 27.0 GW a year; solid-state units reach 9.0% of new medium-voltage capacity	8.18	8.93%
High	Additions 12% above base; solid-state adoption 35% faster	9.21	10.22%

The high case assumes new transformer factories reach full output on time and 800 VDC designs spread beyond the first AI campuses. On-site generation is the main swing factor, because a self-generating campus needs a smaller grid transformer.

Competitive Insights: Who Leads the Data Center Transformer Market?

• Hitachi Energy
• Siemens Energy
• GE Vernova (Prolec GE)
• Schneider Electric
• Eaton
• Hammond Power Solutions
• HD Hyundai Electric
• Hyosung Heavy Industries
• LS Electric
• Mitsubishi Electric
• Toshiba Energy Systems & Solutions
• WEG
• DG Matrix

The three largest suppliers, Hitachi Energy, Siemens Energy and GE Vernova, together hold about 27% of the Data Center Transformer Market in 2025 (DC Market Insights estimate, based on their position in power transformers, which make up 58.0% of the market, and GE Vernova’s distribution transformer lines through Prolec GE). GE Vernova completed its purchase of the remaining 50% stake in Prolec GE for USD 5.275 billion in February 2026 (Source: GE Vernova press release); Prolec GE expected about USD 3 billion of revenue in 2025, serving markets where electricity demand growth is driven in part by data centers. Hammond Power Solutions reported record 2025 sales of CAD 898 million, up 13.9%, with backlog 122% higher than a year earlier and growth tied in part to data center expansion. Hyosung Heavy Industries booked about KRW 9.3 trillion of new orders through August 2026, already above its total for all of 2025, and formed a dedicated data center business team. Schneider Electric, Eaton, HD Hyundai Electric, LS Electric, Mitsubishi Electric, Toshiba and WEG compete in power and distribution transformers, and DG Matrix in solid-state units.

Recent Developments

• In February 2025, Eaton announced a USD 340 million investment to convert a facility in Jonesville, South Carolina, into a three-phase transformer plant, with production expected to begin in 2027 (Source: Eaton press release).
• In August 2025, Eaton completed the acquisition of Resilient Power Systems, a developer of solid-state transformer-based technology with application potential for data centers (Source: Eaton press release).
• In September 2025, Hitachi Energy announced a USD 457 million investment in South Boston, Virginia, that will make the site the largest manufacturing site for large power transformers in the United States (Source: Virginia Governor’s Office news release).
• In February 2026, GE Vernova completed its USD 5.275 billion acquisition of the remaining 50% stake in Prolec GE (Source: GE Vernova press release).
• In July 2026, HD Hyundai Electric signed a framework agreement worth up to KRW 1.12 trillion with a global big tech company for distribution and high-voltage equipment for North American data centers through 2028 (Source: The Korea Times news report).
• In September 2026, Hyosung Heavy Industries signed KRW 386.5 billion of 765 kV and 345 kV transformer contracts with two US big tech companies for new AI data centers (Source: Asia Economy news report).

We follow these orders, factory investments and power architecture changes as they happen in our data center industry updates.

Methodology: How We Built the Data Center Transformer Market Model

DC Market Insights built this market bottom-up from 16 annual capacity cohorts (2020 to 2035). Each year weights 45% of that year’s IT capacity completions and 55% of the next year’s. Power transformers are priced per MW of IT load (USD 0.10 million in 2020, USD 0.14 million in 2025, USD 0.16 million by 2035). Medium-voltage transformers are sized at 1.62 MVA per MW in 2020, falling to 1.55 MVA by 2035, and priced per MVA; low-voltage dry-type transformers fall from 0.43 MVA per MW in 2025 to 0.31 MVA by 2035. Solid-state transformers take a rising share of new medium-voltage capacity from 2027 at a premium that falls from 3.5 times a conventional unit in 2025 to about 2.1 times by 2035, and replacement and upgrade spending is added on the installed base. Every split sums to the market total. Because no major supplier we reviewed reports data center transformer sales separately, the result was checked against bounds: the power transformer line equals our substation model, the medium-voltage price sits inside a public distribution transformer price range, and the roughly 76 GVA of medium-voltage capacity the model installs in the United States between 2025 and 2030, about 38 GW of served load if half is redundant, is broadly consistent with the 12.6 GW to 72 GW of transformer capacity for power delivery units that NREL expects data center demand may add by 2030. The analyst named on this page built the model, and the reviewer checked the arithmetic, the sources and the dates before publication.