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It is the responsibility of all registered users of the Human Mortality
Database (HMD) to give proper credit to the institutions and/or individuals
who have created the data being provided or transmitted here. Proper
citation is necessary whether the data in question are quoted in formal
publications or in other contexts. The following comments are intended
to assist users by providing information about HMD data sources and
by offering suggestions for appropriate citation procedures. Please
note, however, that ultimate responsibility in these matters resides
with the user alone, under the terms of the
User Agreement.
Raw Data versus HMD Estimates
It is important to distinguish between two types of data included in
the HMD. First, there are several kinds of raw data for each population,
which serve as inputs for all subsequent calculations. Second, there
are data of various sorts that are original to the HMD, having been
generated according to techniques that are fully described in our Methods
Protocol. In the former case, it is important to acknowledge the institutions
or individuals responsible for creating and/or publishing the raw data:
in these circumstances, the HMD is merely transmitting the data from
its source to the user. Thus, it is only in the second case that it
is appropriate to give credit to the HMD as the source (i.e., author)
of the information provided here.
Identifying the Correct Data Source
The user can successfully determine whether a particular number is being
transmitted from an external source or whether it is original to the
HMD using the following guidelines:
Input Data
Generally, the Input Data have been extracted from other sources,
which are clearly documented using a system of reference codes.
The HMD should not be cited as the source of such information,
but only as an intermediary
that has transmitted the data from its source to the user.
Complete Data Series
Births: All birth counts come from an external source, and
the HMD is merely transmitting the information to the user.
The user should identify and cite the original
source, merely acknowledging the HMD as the intermediary. There are
two ways of identifying the original source of such data. First, the
user may consult a complete list of sources for a given population by
means of the link to "Data sources" found near the top
of each country page. This list is organized by data type (births,
deaths, etc.). In most cases, the source of birth counts reported
in HMD should be readily apparent. However, if questions remain after
consulting this list, the user should consult the Input Data,
in which the source of every raw data point is clearly noted.
Deaths: The death counts presented in the "Complete Data Series"
section of country page may or may not have been manipulated in various ways.
For citation purposes, we must distinguish between two cases:
Some death counts are presented without
alteration. Thus, they are identical to the Input Data,
and the proper citation procedure is the one given above
for birth data. For death data by Lexis triangle, this case is
relatively rare: it occurs only when the original source contains
death counts classified by single year of age, year of occurrence,
and year of birth, and where there are no reports of deaths with
age unknown (for a given calendar year). Most death counts undergo various
alterations, which may be slight or substantial in nature. Briefly,
there are two kinds of manipulations applied to raw death
counts in the HMD: i) assigning deaths of unknown age to specific
ages, and ii) splitting aggregate death counts (in various formats)
into data organized by Lexis triangle. In these situations, the
numbers are original creations of the HMD, which should thus be
acknowledged as the source of the data.
The data for a given population may comprise one or
both types of death counts (i.e., unaltered raw data and/or original
HMD estimates). The simplest method of distinguishing
between these two types is to observe whether a number contains some
fractional deaths. That is, raw data are expressed as a whole number
of deaths, whereas estimated death counts typically contain some fractional
element. This method is not infallible, as the fractional part of
an estimate could be zero just by chance: since death data are formatted
with 2 decimal points, this should occur at random with a frequency
of 0.01. However, by inspection of surrounding data points, there
should in general be no ambiguity about this issue. In cases of lingering
doubt, the user should consult the HMD Input Database and examine
the raw data directly.
Population size:
For ages 80 and above, most of the population estimates reported in the
"Complete Data Series" section are original creations of the HMD and
should be cited accordingly. One exception pertains to cohorts who would
be aged 80-89 at the end of observation (see Figure 6 of the
Methods Protocol). A second
exception includes a few countries (i.e., Sweden, Denmark, Norway,
Finland, and Iceland) for which we use official population estimates
for ages 90 and older at the end of the data series (see footnote 16 of
Methods Protocol).
Below age 80, population estimates may come directly from an external
source, or they may be unique to the HMD. As with death counts,
it is possible to determine whether a number comes from an external
source or was created expressly for the HMD by observing its decimal
part: whole numbers usually indicate that a number is taken from
some other source, whereas a non-zero fraction (i.e., anything other
than "00" after the decimal point) is a sign that the number
is a product of the HMD itself.
Exposure-to-risk, death rates, life tables, or life expectancy at
birth: All such data are original creations of the HMD, which
should thus be cited as the unique source of the information.
Choosing a Bibliographic Citation
HMD Estimates
As described above,
proper citation practice requires that a user determine whether
numbers obtained through the HMD come from an external source or whether
such data are original creations unique to this database. If the user
concludes that the data in question should be attributed to the HMD
itself, we suggest the following format for a bibliographic citation:
Human Mortality
Database. University of California, Berkeley (USA), and Max Planck
Institute for Demographic Research (Germany). Available at
www.mortality.org
or www.humanmortality.de
(data downloaded on [date]).
If you choose another citation format, please be sure that
it includes the full name of the database (Human Mortality Database),
the full names of both institutional sponsors (University of California,
Berkeley, and Max Planck Institute for Demographic Research), one
or both of our Internet addresses
(www.mortality.org
or www.humanmortality.de), and the date accessed.
Data from external sources
For data from an external source, which are merely
transmitted via the HMD, the user
should choose an appropriate citation based on standard practice. The
citation given in the list of "Data sources" for each population
may be used as a guide, but it should not be considered authoritative.
It is appropriate in these situations to acknowledge the HMD as the
intermediary through which the data were obtained. For example, a bibliographic
citation for death counts in the United States might be as follows:
National Center
for Health Statistics. Vital Statistics of the United States,
Volume II: Mortality, Part A. Washington, D.C.: Government Printing
Office, various years. (Data obtained through the Human Mortality
Database, www.mortality.org
or www.humanmortality.de,
on [date].)
User's responsibility
Finally, please remember that proper citation of data
obtained through the HMD is the responsibility of the user alone,
as stated clearly in the User Agreement. However, if you still
have questions or comments about citation procedures
after reading these guidelines, please write to us at
hmd@mortality.org.
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