Helen Samhan, executive director for the Arab American Institute (AAI), told Aljazeera.net her group had always disputed the numbers collected through the national census because "their approach does not capture all the numbers of our growing community".
She blames the methodology used by the census and the lingering fear among Arabs of being "listed" in the wake of the 9/11 attacks.
AAI, quoting pollsters Zogby International, said there were approximately 3.5 million people of Arab ancestry living in the US.
Zogby's census methodology relies on phone polling, whereas the Census Bureau uses mail out forms for individuals to fill out and send back to the bureau.
Brittingham: Accuracy depends
on how many filled out the forms
The official 2000 census form asked individuals to describe their ancestry or ethnic origin. It also asked that individuals check off which race they identified with.
Arab ethnicity is not listed as a race in this section. Those of Arab ancestry are therefore required to check off "other" on the form and write out what race they most identified with.
Angela Brittingham, a demographic research analyst at the US Census Bureau and one of the report's authors, defended the findings.
"While organisations like AAI target Arab Americans and call that specific community, the US Census is a national project, so it only makes sense to use mail out forms.
"This is why we have worked closely with Arab American organisations, so they can help and get the word out to their community to fill out the census so their community can be recognised," she told Aljazeera.net.
She accounted for the discrepancy in numbers by explaining that the statistics in the report provide a portrait of the info the bureau receives - an approximation and not an exact figure.
"Like I tell people time and time again, that information we receive and analyse highly depends on people actually filling out the long form and mailing it back to us."
Fear still exists
The discrepancy in findings may also be due to many not willing to fill out a census form for fear they may be targeted as terrorism suspects because of their race, Arab American advocates say.
Information passed on to US
agencies kept many Arabs away
In 2002, the US Census Bureau disclosed detailed information to the US Customs Service about the Arab American community, and in 2003, the same information was disclosed to the Department of Homeland Security and the Bureau of Customs and Border Protection.
"Actions like these play a big factor in filling out the actual census," says Nawar Shora, legal adviser for the American Arab Anti-Discrimination Committee (ADC).
"Mistrust is a factor now."
While the 2000 census was filled in 1999, before the 11 September 2001 attacks and the ensuing fallout, Shora says there has always been this fear among some in the Arab American community because of the negative stereotypes that exist about the community.
Nawar told Aljazeera.net that he hopes when the next census approaches in 2010, Arab Americans will overcome this fear and actively participate.
"We have strength in numbers," Nawar says. "And that is why we must, as a community, take the census seriously and fill it out. This will add credibility on a societal front for our community."
AAI and ADC are working closely with the census bureau to make sure their community is not undercounted.
AAI stresses that the census helps in determining the allocation of funds to communities in need of it and determines the mapping of congressional districts that "ensure proper representation in Congress".