Report E008R01

US EGG PRODUCTION DATA SETSamara Mendez1

EXECUTIVE SUMMARY Tracking the capability of the egg production industry to supply the food industry
with enough cage-free eggs to meet retailers’ and restaurants’ animal welfare commitments is important toindustry groups and farm animal advocacy organizations alike. In this project, we synthesize an analysisready data set that tracks cage-free hens and the supply of cage-free eggs relative to the overall numbersof hens and table eggs in the United States. The data set is based on reports produced by the UnitedStates Department of Agriculture (USDA), which are published weekly or monthly. The data will be updated
periodically as new USDA reports are released. We supplement these data with definitions and a taxonomyof egg products drawn from USDA and industry publications. The data include flock size (both absolute andrelative) and egg production of cage-free hens as well as all table-egg-laying hens in the US, collected tounderstand the impact of the industry’s cage-free transition on hens. Data coverage ranges from December
2007 to present. Initial analysis of cage-free trends shows that, as of the most recent version of this report,
29.2% of all table-egg-laying hens lived in cage-free systems. This figure represents an increase of 26
percentage points over the entire sample period of December 2007 to February 2021.
PUBLISHED August 11, 2019 | REVISED March 8, 2021

1
https://orcid.org/0000-0002-8179-744X
The Humane League Labs, Rockville, MD, USA
smendez@thehumaneleague.org

All files related to this project are available in the associated OpenScience Framework repository at https://osf.io/z2gxn/.
This work is licensed under the Creative Commons Attribution
4.0 International License. To view a copy of this license, visit
http://creativecommons.org/licenses/by/4.0/ or send a letter to Creative
Commons, PO Box 1866, Mountain View, CA 94042, USA.

CONTENTS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Results and Conclusion . . . . . . . . . . . . . . . . . . . . . . . . 5
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

INTRODUCTION
Egg production in the United States (US) changed greatly
over the twentieth century. Prior to the mid-twentiethcentury, egg-laying hens primarily lived on family farms
and roamed outside and in chicken coops for safety andsleeping. Egg farms began to grow in size in the 1940s and1950s, and farmers transitioned their chicken flocks intoindoor barns and cages, ostensibly to keep them safe frompredators and diseases [1]. Today the majority of laying
hens living in commercial egg production facilities in the
US are confined to battery cages with approximately 67
in2 (432 cm2 ) of space per bird, the minimum required by
the national egg producer cooperative United Egg Producers. Cages represent a significant animal welfare concern
because they prevent hens from performing their natural
behavior and can increase the risk of osteoporosis and body
injury from feather pecking and cannibalism [2].
Animal protection groups have focused on campaigningagainst battery cages for several years, using corporate negotiation, positive and negative publicity campaigns, andlegislation to shift the egg production system away fromthese cages. In 2015, California’s Proposition 2, named“Standards for Confining Farm Animals,” took effect1 and
1 Proposition 2 passed in 2008 and was implemented in 2015. The

statute prohibited the confinement of farm animals in structures thatprevent them from lying down, standing up, fully extending theirlimbs, and turning around freely [3]. The vague wording of Proposition 2 allowed for “enriched cages” (larger cages with features likeperches and scratching areas), and some producers switched fromconventional cages to enriched cages as a means of compliance with
the new law [4]. In 2013, the California Department of Food andAgriculture updated their statutes to require that all eggs either produced or sold in California be sourced from hens with at least 116
in2 (748 cm2 ) of floor space in their enclosure [5]. In 2018, Proposition 12, another California ballot initiative entitled “Preventionof Cruelty to Farm Animals Act,” was adopted to further update
the standards of confinement for the farm animals producing foodsold in California [3]. This bill improved upon the vague languageof Proposition 2 and expanded upon the 2013 statutes to require atleast 144 in2 (929 cm2 ) of floor space in barns without cages [6].

many major food companies, including Costco and institutional food service providers Sodexo, Aramark, andCompass Group, pledged to source cage-free eggs by dates
in the near future. These events drove many other foodservice corporations to make similar commitments. To
date, about 400 retailers, restaurants, and food service institutions with US operations have made commitments to
exclusively source cage-free eggs for their supply chains by
2026 [7].
This report monitors the progress of the egg industry
in transitioning their flocks away from battery cages into
cage-free systems by tracking the production of cage-free
eggs. Understanding productive capabilities is crucial fordownstream food companies looking to source cage-free
eggs and for animal protection groups seeking to facilitate the transition away from cages. To that end, this data
set tracks monthly absolute and relative flock size and egg
production in the US starting in August 2016, and relative flock size collected at irregular intervals from 2005 topresent. Data are gathered from three United States Department of Agriculture (USDA) reports on cage-free andoverall egg production in the US: the weekly Egg Markets
Overview report [8], the Monthly USDA Cage-Free Shell
Egg report (hereafter “Cage-Free Egg” report) [9], and themonthly Chickens and Eggs report [10]. We supplement
the data with clarification of terms and definitions usedin the USDA reports and by some industry groups, andwe conduct initial analysis of the data by examining thepercentage of hens in cage-free housing systems over time.
BACKGROUND
Modern commercial egg production creates a variety ofdifferent egg products using a number of different production processes. The egg products considered in this data
set are classified over two dimensions in the USDA reports:
production process and product type. Each cell in Figure
1 represents a unique type-process classification. Production process covers two overlapping processes: housing
type (“cage-free” or “caged”) and animal management (“organic” or “non-organic”). The Cage-Free Egg report does
not distinguish other housing systems such as “free-range”
or “pasture” production and the Egg Markets Overview
report only distinguishes these systems in data collected
after 2016, so we do not include them in the report or egg
production data set other than to discuss their relation to
cage-free and caged systems. “Product type” encompasses
two types of egg products: “table” eggs and “hatching”
DOI 10.31219/OSF.IO/WTA3Q |2

Figure 1 Taxonomy of eggs by product type and production process

eggs. Table eggs can be further divided into “shell” eggs
and “processed” eggs. This data set tracks production at
the table egg level because neither the Cage-Free Egg report
nor the Egg Markets Overview report disaggregates production data into shell egg and processed egg production;2
however, we include these sub-types in the taxonomy forcompleteness. The terms used here for classification are encountered in the USDA data as well as across egg industry
publications, and we clarify these terms in more detail asfollows.
Table eggs are all eggs sold to be used as food ingredients. Shell eggs are purchased still in their shells, while
processed eggs are broken out of their shells and sold ina variety of processed forms including liquid, frozen, ordried/powdered. Hens who produce table eggs meant for
consumption are known as “table egg type layers” (hereafter “table layers”). “Flock size” provides the estimatednumber of hens living in an operation at a given point intime. A “lay rate” (also called “rate of lay” or “hen-day egg
production” in other USDA and industry publications[11]) refers to the number of eggs produced over a given
time period by a specific number of hens. The USDA uses
different time periods in different reports: for example, theChickens and Eggs report records the lay rate as the number
2 Note that while the Cage-Free Egg report bears the full title “Monthly

USDA Cage-Free Shell Egg Report,” the production data are reported at the table egg level. All price data in this report are given at
the shell-egg level.

of eggs produced by 100 hens in the reported month, while
the Cage-Free Egg report gives the more common daily lay
rate expressed as a percentage.
Hatching eggs are fertilized eggs used for the reproduction of chicken flocks, either layer hens (both table andhatching) or chickens raised for meat (“broilers”). Hens
who produce hatching eggs are called “hatching egg typelayers” (hereafter “hatching layers”). The reproductive
purpose of hatching layers necessitates that females andmales are housed together in aviary or barn systems which,as discussed below, are considered cage-free housing. US
hatching layers are distinguished only by breed and theirhousing systems are not classified in the same manner astable layers. Public data provide no indication of the proportion of hatching eggs that are destined for cage-freesystems or otherwise.
Cage-free hen housing systems offer hens more space tomove freely through their environment and opportunities
to forage, perch, dust-bathe and use a nest area to lay theireggs. The USDA definition of “cage-free” covers a varietyof husbandry systems. The system must allow birds to display natural behaviors, and hens must have the following:
the ability to move in a way that promotes their welfare,protection from predators, and access to litter. Birds areprovided enrichments such as perches, nests, and scratching areas to allow them to perform natural behaviors [12].
Aviary and barn systems are two examples of cage-free housing that allow birds to freely roam inside the buildings. In
barn systems, birds generally live on one level, while aviary
systems have multiple levels for perching [13]. Cage-free
eggs may be produced by either non-organic flocks or “certified organic” flocks. The USDA requirements for organic
certification include organic feed requirements as well as
housing and welfare requirements. These housing and welfare standards are similar to the requirements for cage-freecertification, so all certified organic eggs can be classified as
cage-free [14]. Similarly, free-range housing requirements
defined by the USDA and pasture-raised housing requirements defined by third-party certifiers like American Humane and Certified Humane3 encompass and exceed therequirements of cage-free systems [12; 15; 16]. However,since neither the Cage-Free Egg report nor the Egg Markets Overview report consistently disaggregates cage-free
production data into more production processes than “organic” and “non-organic,” we will not detail free-range and3 At this time, the USDA does not define or grade eggs marketed as

pasture-raised.
DOI 10.31219/OSF.IO/WTA3Q |3pasture-raised production processes in our final data.4
METHODOLOGY
In this section, we describe our data collection methodology. We begin with gathering information about how the
USDA collects data from egg producers to compile theirdata products. Next, we describe in detail our methodology for transcribing, cleaning, and analyzing the final
data.
Monthly reports

The Cage-Free Egg report and the Chickens and Eggs reportare both produced monthly, published in the first and third
weeks of the month, respectively. These reports provide
egg production numbers from the previous month, so wetimestamp the data with the observed month as stated in
the report.5 These reports are produced by the USDA’s
Agricultural Marketing Service (AMS) and National Agricultural Statistics Service (NASS), respectively. The CageFree Egg report is compiled by the Des Moines, Iowa officeof the AMS’s Livestock, Poultry, and Grain Market News
department, while the Chickens and Eggs report is produced by the Livestock Branch of NASS [17; 18]. The
first Cage-Free Egg report was issued on September 19,
2016 and covers the month of August 2016, while the
Chickens and Eggs report has been produced since 1933.
Archived and current copies of both reports are available
on the USDA’s Economics, Statistics and Market Information System website, which provides a search portal
for archives of reports produced by five different USDA
agencies [19]. Archived reports referenced in this data
set are also available in the directories data/raw/cagefree-egg-report and data/raw/chickens-and-eggsreport of the Open Science Framework (OSF) repository at https://osf.io/z2gxn/, which will be updated witharchived copies of subsequent reports according to theirrelease schedule. All subsequent references to directories
and files refer to this OSF repository.
The NASS uses a monthly survey to collect mandatory
production data directly from egg producers with flocks
4 The authors of these reports have confirmed in personal communi-

cations that hens living in free-range and pasture production systems
are categorized as cage-free for the sake of the data in their reports.
5 The AMS collects data for the Cage-Free Egg report from participants
once per month, although the reports do not indicate a referencedate, so it is not clear which day of the month the data represent.
We arbitrarily assign the observations to the last day of the observed
month.

of at least 30,000 layers for the Chickens and Eggs report.
This report records data on eggs produced by hens in commercial facilities as opposed to backyard flocks. The survey
instrument provided by the NASS is archived under the filename data/raw/Chickens-and-Eggs-report-surveyinstrument.pdf. The AMS collects data for the CageFree Egg report directly from producers who have volunteered to provide production information. The AMS attempts to contact all US commercial egg producers, but as
participation is voluntary, some producers do not respondto the survey. The AMS estimates that the nonresponsive
producers manage 5-10% of the US commercial egg laying
hens. The authors note that operators of smaller facilities are less likely to respond, and because free-range andpasture housing systems are more likely used at smaller operations, the number of cage-free layer hens may be slightly
underestimated in the Cage-Free Egg report. The data
presented in these reports therefore represents the lower
bound of cage-free egg production and flocks sizes in the
US. A monthly average of weekly egg production numbers in the Cage-Free Egg report are constructed from theproducer-reported number of cage-free hens and daily cagefree lay rates multiplied by seven days,6 while the Chickens
and Eggs report constructs monthly egg production frommonthly lay rates. To account for time period differences
when cleaning and analyzing the data, we convert weekly
cage-free egg production to monthly by multiplying thedata by the fractional number of weeks in the observed
month. These differences in aggregation may affect statistical analysis of constructed variables such as the percentage
of cage-free eggs to total egg production by averaging out
some of the variance.
Weekly report

The Egg Markets Overview report is produced by the Agricultural Analytics division of the AMS, independently of
the Cage-Free Egg report, and provides a weekly snapshotof different topics in the US egg market. The report has
included the percentage of hens in different housing systems at irregular intervals several times a year since 2016,
publishing data that spans back to 2007; coverage of this
topic in weekly reports has increased since 2019 to roughly
monthly. We time stamp observations from these reports
6 Personal communication with the authors indicates daily cage-freelay rates are based on the monthly lay rates published in the Chickens
and Eggs report with a downward adjustment to account for the
lower productivity of cage-free hens.

DOI 10.31219/OSF.IO/WTA3Q |4with the month-day value stated in the text or table notes.
The USDA publishes only the most current version of thisreport, so we provide the reports that inform this data set
in the directory data/raw/egg-markets-overview. As
with the Cage-Free Egg report, egg producer participationin the Egg Markets Overview survey is voluntary, and the
AMS estimates that producers who manage approximately
90-95% of all US commercial egg layering hens respond to
the survey. Flock sizes in this report are adjusted upward by
5-10% to account for producers’ non-response.7 Because
the Egg Markets Overview data have been adjusted upward
while the Cage-Free Egg report data have not, the percentage data from the Egg Markets Overview report likely provide a more accurate picture of all egg producers in the
US. We include both sources of data for completeness, but
we use data from the Egg Markets Overview report for the
analysis below.
Final data set

The final data set is transcribed from portable document
format (PDF) files into two comma-separated value (CSV)
files for easy use in further analysis. The files named eggproduction.csv and cage-free-percentages.csv are
published in the directory data/final/, accompanied bya data dictionary, named data-dictionary.csv. The
data dictionary describes each variable in both files.
Egg production data The file egg-production.csv is

informed by the Cage-Free Egg report and the Chickens
and Eggs report. We automate data collection from thesereports and analyze the data using a script written withthe statistical programming language R [20]. The automation portion of the code downloads the raw USDA reports,
parses production data from the PDF reports, and wrangles
the parsed data into the final format. The analysis portionof the code conducts initial data exploration. The script
make.R, located in the top level directory of the OSF repository, can be run to execute the entire routine. This routine executes four scripts, located in the directory /code/:
download.R, parse.R, wrangle.R, and analyze.R. Annotations in the make.R, wrangle.R, and analyze.R files
provide details about package dependencies, download
locations, variable units, data sources, and new variable
construction.

From the Cage-Free Egg report, we transcribe the following: the monthly average of flock size for table layers incage-free organic and non-organic flocks and the monthly
average of each flock’s weekly egg output. As discussed
above, we convert egg production to total monthly production. Because the reported egg production numbers
are constructed as a function of flock size and lay rates, weomit lay rates to streamline the final data set.8 From the
Chickens and Eggs report, we supplement cage-free statistics with the flock size and monthly output of all table andhatching layers. We include the number and output of
hatching layers because changes to the overall number oftable layers will cause changes in the number of hatchinglayers required for reproduction. The unit of observationin the final data set is a date-product type-production process combination.
Cage-free percentages The file used for analysis, cagefree-percentages.csv, includes data transcribed fromthe Egg Markets Overview reports and calculations performed on data in the file egg-production.csv. We construct this file to analyze basic patterns in the data; namely,
we focus on the relative number of hens living in cage-freesystems compared to the whole flock, an important statistic
for understanding the transition away from battery cages.
The Egg Markets Overview report publishes these percentages directly, and we construct similar percentages using
the number of cage-free hens reported in the Cage-Free
Egg report relative to the number of all table layers in the
US provided by the Chickens and Eggs report. We also use
data from these two reports to calculate the monthly percentage of cage-free eggs to relative to total egg production.
Complete details are provided in the annotated R script
analyze.R.
RESULTS AND CONCLUSION

7 The adjustment factor varies with housing type. Details about thisInitial exploration of cage-free egg production in the US
in Figure 2 shows an increase in the percentage of hens in
cage-free housing over time as reported in the Egg Markets
Overview reports. From December 2007, when data are
first available, to February 2021, the most recent data at
the time of this revision, the percentage has increased by 26
points. The industry’s expansion of their cage-free flocks
accelerated in 2015 and has continued consistently in thesubsequent years.

procedure were obtained from AMS staff in personal communication.

8 Interested users can reconstruct these rates if needed by dividing

monthly egg production by monthly average flock size.
DOI 10.31219/OSF.IO/WTA3Q |5

Figure 2 Percentage of hens in cage-free housing from December 2007 to February 2021 [8]. Data are available athttps://osf.io/z2gxn/.

Through the creation of this report, we have increased
our knowledge of the methodology underlying the USDA
reporting on cage-free egg production. Any further information obtained or updates to the methodology will be
included in future version of this report. Further, the associated data set and archives will be updated periodically;
this report should be regarded as a living document. Future
projects using these data may include supply forecasting,demand analysis, and expansion of the data to other countries. We provide this data set to researchers wishing toconduct independent analysis, and we welcome questions
and suggestions to improve future updates.
REVISION HISTORY
February 12, 2020

• Revised “more than 400 food businesses” to “about
400 food businesses.”• Added OSF repository url to caption of Figure 2.
• Non-substantive copy edits and formatting changes.
May 29, 2020

• Updated latest cage-free percentages.
• Restructured and updated the methodology section
to include new details about USDA data collection
methods.

• Updated Figure 2 to reflect new metholodogy details.
• Non-substantive copy edits.
March 04, 2021

• Updated latest cage-free percentages.
March 08, 2021

• Updated latest cage-free percentages.
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(2017). A Decade of Progress toward Ending the Intensive Confinement of Farm Animals in the UnitedStates. Animals, 7 (12), 40. https://doi.org/10.339
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