Around the world, countries from Afghanistan to Papua New Guinea to the United States are taking part in their decadal census, leading the UN Population Fund (UNFPA) to select the theme “Everyone Counts” for World Population Day 2010, which was celebrated on July 11.

Everyone has the right to be counted, because “censuses and population data play a critical role in development and humanitarian response and recovery,” said UNFPA Executive Director Thoraya Ahmed Obaid in her World Population Day message. Obaid added that “with quality data we can better track and make greater progress to achieve the Millennium Development Goals, and promote and protect the dignity and human rights of all people,” especially among vulnerable populations like women, girls, the poor, and the marginalized.

USAID similarly supports quality data collection, which it says plays a critical role in advancing voluntary family planning in the developing world. For the last 25 years, USAID has funded the Demographic and Health Surveys (DHS) program, which collaborates with national health ministries to collect data on family planning, child and maternal health, disease prevalence, and other health indicators.

This invaluable data is made freely available for public use, which can foster new research in the field and stimulate innovative approaches to addressing public health issues. Praising the DHS program, Gapminder Foundation Director Hans Rosling told a Wilson Center audience last year that “statistics should be the intellectual sidewalks of a society, and people should be able to build businesses and operate on the side of them.”

Accurate census counts are also important elements of “good governance, transparency and accountability,” said UN Secretary-General Ban Ki Moon in his World Population Day message. “Population data helps leaders and policy-makers to make informed decisions about policies and programmes to reduce poverty and hunger, and advance education, health and gender equality,” he said.

But no one is suggesting that coming up with reliable population data is an easy task. As Sean Peoples and Elizabeth Leahy point out in the May/June 2009 issue of World Watch magazine, issuing population projections can be a risky business:

In the 2008 Revision of World Population Prospects, the UN Population Division projects that our planet will grow to 9.15 billion people by 2050. Yet this medium-variant projection is just one of several possible scenarios released in this latest round of number crunching. The low- and high-variant projections—7.96 billion and 10.5 billion, respectively—could instead become reality, given uncertainties in the developing world due to factors such as inconsistent data collection, weak health system infrastructure, and low government capacity.

The goal, then, is to make sure everyone counts.