In a sane world, absolutely. It is valuable for all sorts of government planning to know as many dimensions as possible about the population you serve. But then, the USA is not exactly a sane place, when it comes to issues that relate in some way to immigration.
In a sane world, the population of “undocumented immigrants” – also known as “illegal aliens” would be miniscule. We would enforce our borders, and we would make it very hard for “undocumented” people to find work by imposing severe penalties on those who illegally employ them. But important industries like to employ “illegals”, because you do not have to pay them a normal or a living wage, and if they start to demand decent pay and working conditions, you can call the immigration police and have them deported. Problem solved. So these industries have influenced Federal and State legislatures to be lenient to illegal employers. And now we have 13 million “illegals” and if they were to leave (voluntarily or otherwise) farmers, slaughterhouses and several other industries would be in deep trouble.
In California, we have a large “undocumented” population. We need to count them and include them in our population statistics in order to fairly allocate things like school funding and the number of seats in the Federal House of Representatives. And that is precisely why Republicans do not want to count them. They want to citizenship question added to the Census because it will make the “undocumented” afraid to participate in the Census.
In theory, the rules for the Census should alleviate that fear. The Census data is confidential, and individual records are not to be shared with the public or other government branches. But when the head of the Census department is a Republican, how much do you trust that that confidentiality will hold?
So as a California Democrat, I have to agree with our state officals that this question should not be asked in the 2020 Census.
Immigration is a big tangle of interacting difficult problems made worse by bungling politicians over decades. Almost every suggestion you hear that sounds simple is counterproductive.
One of these days, I will write a long blog post about what I think could be done to start making things better, but not this week.