Robert Anderson may know more about death than anybody else in the country.

Anderson is chief of mortality statistics for the Centers for Disease Control and Prevention. Information about death flows into his suburban Maryland office from all over the country, detailing not only how many Americans have died - the tally for 2013 was 2,596,993 - but also the causes of those deaths.

Researchers use the information to learn what kills Americans, and public officials use it to craft policies to improve health and safety.

On the best death certificates, the information is accurate and complete. That would mean, for example, that the death certificate would say not only that someone had died of a drug overdose but also that the drug had been heroin. If the departed had died of cardiac arrest, the certificate would say that death resulted from a heart attack and it would disclose that the person had been a lifelong smoker and overweight.

Unfortunately, many death certificates are incomplete or inaccurate. With thousands and thousands of cases, such gaps can translate into a faulty understanding of mortality and affect how money is spent on research and prevention.

"You might be developing programs that aren't addressing the real problem, in which case you are wasting money instead of really targeting it where it needs to go," Anderson said.

Unlike most countries, the United States does not have a centralized office of vital statistics. Instead, all 50 states - plus the District of Columbia and New York City, as well as five U.S. territories - have their own offices, which collect information on births and deaths and send it to Anderson's office.

With some prodding from the CDC, states have begun improving the accuracy and timeliness of the data, mainly through the adoption of electronic systems.

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A study published last year in the Journal of Studies on Alcohol and Drugs found that death certificates related to motor vehicle accidents often failed to mention the involvement of alcohol.

From 1999 to 2009, death certificates reported that alcohol was involved in 3.3 percent of traffic deaths. By contrast, the federal Fatality Analysis of Reporting System, which collects information on car accidents, reported alcohol involvement in more than 20 percent of fatal accidents.

Similar studies have noted the underreporting of conditions such as dementia and diabetes.

Medical researchers and statisticians say people who complete death certificates often leave out some details because they want to spare relatives from distressing information. They also attribute deficiencies in death certificates to the absence of autopsies in the vast majority of cases and to insufficient training of those who fill them out.

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Death certificates are largely standardized across the country, but the people responsible for filling them out vary from state to state and even jurisdiction to jurisdiction.

The apparent cause of death is the main determinant of who will fill out a death certificate. With nonnatural deaths, including homicides, suicides and accidents, as well as with infant deaths and deaths from undetermined causes, it is generally up to a medical examiner or coroner to fill out the death certificate.

For the vast majority of people who die a natural death, the last medical provider attending the deceased - usually a physician, a physician assistant or a nurse - fills out the death certificate. But most physicians aren't trained how to do this correctly and comprehensively, Anderson said.

It doesn't help that in most cases, they must fill them out without the benefit of an autopsy, which is the most definitive method of determining the cause of death but costs several thousand dollars.

As a result, many death certificates lack the specificity that would help researchers studying the prevalence and causes of deaths.

The details matter.

Complete and correct statistics on death are essential for understanding fatal diseases and injuries, said Marcus Nashelsky, president of the National Association of Medical Examiners and a professor of pathology at the University of Iowa.

"Research using local, regional, state or national death statistics is a vital component of public health activities - ranging from education and prevention strategies for heart disease, diabetes, infectious diseases, injuries and so on," he said.

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The CDC's Anderson, who trains hospital workers to fill out death certificates, said medical residency programs should provide such training and doctors should be required to take online courses in death certificates as part of their continuing education requirements, although it is up to medical licensing boards in each state to establish such requirements.

Several states are trying to improve the quality of reporting on death certificates, most notably through state-run electronic systems. According to the National Association for Public Health Statistics and Information Systems, 35 states plus the District and New York City have searchable, electronic death certificate databases.

In those jurisdictions, a funeral director typically begins the death certificate process by providing identifying information about the deceased. After that, the system alerts the medical provider who last saw the patient to fill in the cause and manner of death.

Anderson's staff at the CDC is developing an online service that will walk providers through the process of filling out death certificates. Melissa Bird, chief of the Iowa Bureau of Health Statistics, said her agency's electronic system enables it to track pending certificates and to nudge or assist medical providers who are lagging.

Since Iowa's system was introduced in 2014, she said, the average time it takes to complete a death certificate has been cut from more than two weeks to six days.

A speeded-up process also helps survivors, who often need death certificates to gain access to financial accounts, safe deposit boxes, insurance proceeds and more. In some states, a death certificate is needed before burial or cremation.