Jonathan Wajskol, an Italian graphic designer who moved to the US about three decades ago, has a life with all the hallmarks of an immigrant success story: graduate studies at an American university; a successful international firm with partners in Milan and Beijing; and a residence in Greenwich Village where he lives with his wife and two children.
One thing he does not have, however, is American citizenship - and that is a deliberate choice. He has a green card, but he has never applied for citizenship and is not interested. His reasons, he said, go to the heart of his identity. "I would feel that if I get the American citizenship, I would feel a little less Italian," he explained. "I really don't feel American."
For many people around the world, a US passport is a near-sacred goal, and given half a chance to get one, they would eagerly seize it.
But even as legions in the US and abroad pin their hopes on becoming American, there is a seemingly contradictory truth: that millions of people who are in the country legally, and stand on the threshold of citizenship, never take that next step.
According to some estimates, about 40 per cent of all people who hold green cards, the gateway to citizenship, do not naturalise.
Of those, many may want to apply but are deterred by a variety of reasons, including the US$680 application fee or the requirement that most applicants must prove they can read, write and speak basic English, immigrants' advocates said. Some countries - including China, Japan and Iran - generally do not permit their citizens to acquire a second nationality, forcing a difficult choice.
But alongside those potential applicants, there is a vast population of green card holders who simply don't want to be American.
For Wajskol, whose wife and children are US citizens, the question of naturalisation bubbles up from time to time. He even filled out the paperwork, but never followed through.
If he has one misgiving about his position, he said, it would be that he cannot fully participate in the American electoral process.
But aside from that, Wajskol said: "I really have everything that I need. I am treated pretty much just like a citizen."
Lawful permanent residents are eligible to apply for naturalisation after meeting certain requirements, including a minimum length of residency, which for most candidates is five years. In the meantime, they have many of the same rights and obligations as citizens, including permission to work. They are also bound by largely the same tax rules.
But in addition to limited or no voting rights, lawful permanent residents cannot make their home in a foreign country or remain outside the US for extended periods of time, except in specific circumstances. They are ineligible, in many cases, for Civil Service jobs and certain government assistance. They can sponsor fewer types of family members for visas than can citizens. And they can be deported for violating any of a wide variety of laws.
Still, none of these disadvantages has been enough to compel many lawful permanent residents to stand and take the Oath of Allegiance.
Xiaoping Wang, who was born in Beijing and moved to New York City in 1994, is the owner of China Sprout, a company that distributes Chinese cultural and educational products. She has a green card yet no urge to naturalise.
"I love New York, I love the United States, I love everything here and the opportunity that I have in this country," said Wang, who is married to a German. "I just don't see the advantage" of being naturalised, she added.
The number of naturalisations in the US has fluctuated in recent years. After reaching a record high of nearly 1.05 million in 2008, the number plunged to about 620,000, or about 41 per cent, in 2010 but started climbing again, topping 757,000 last year, according to federal statistics.
Still, that number is a mere fraction of the total population eligible to apply for naturalisation. Of the estimated 13.3 million green card holders living in the US at the beginning of 2012, about 8.8 million were eligible to naturalise, according to the Homeland Security Department.