As the Senate immigration reform bill heads into the amendment process this week, one aspect sponsors hope to preserve is a way to cut down the sometimes decades-long backlogs for immigrant visas.

Two major components of the bill include a plan to trim two categories of family-sponsored visas — including the one with the longest waits — and a provision that no newly-recognized immigrants can seek permanent legal status unless existing backlogs have cleared. The idea would be for these backlogs to clear in ten years, after which people who have obtained provisional legal status under the bill could then get in line.

It's an ambitious plan. There are more than 4 million hopeful green card holders waiting in backlogs now, being sponsored by family members. And although the definition of "family" would be narrower, with an expected increase in legal admissions, there would still be new family members being petitioned along the way. 

Here are the categories with the longest waits for May, according to this month's U.S. State Department Visa Bulletin:

1) Brothers and sisters of adult U.S. citizens from the Philippines, a wait of more than 23 years (petitions filed October 1, 1989).

This category stands to be eliminated under the current Senate proposal.

2) Married adult (21 and over) sons and daughters of U.S. citizens from the Philippines, a wait of more than 20 years (petitions filed October 22, 1992).

3) Married adult sons and daughters of U.S. citizens from Mexico, a wait of more than 20 years (petitions filed April 1, 1993)

The Senate bill proposes capping the age for visas in this category at 30.

4) Unmarried adult sons and daughters of U.S. legal permanent residents from Mexico, a wait of 20 years (petitions filed May 1, 1993). 

The Senate bill proposes removing annual limits on green cards for spouses and minor children of legal permanent residents. Immigrants in this category from the Philippines, Mexico, India and China currently face a two-year backlog. But unmarried 21-and-over children of legal residents would still have to wait.

The unmarried adult sons and daughters of some U.S. citizens aren't very far ahead in line, either, with those from Mexico waiting since August 1993, and those from the Philippines since June 1999. 

Why do hopeful immigrants from some countries wait much longer than others? Under the current system, each nation gets the same percentage from a pool of family and employer-based visas allotted each year, regardless of demand. In countries such as Mexico, the Philippines, China, and India, where there is the most demand for family reunification in the U.S., this translates into large numbers of people waiting for a relatively small number of visas. So they wait longer.

What the bulletin shows are the dates on which their paperwork went into the system. Having one’s priority date appear in the visa bulletin is good news. But these dates are subject to being pushed back, and often do, resulting in even longer waits.

Immigrants defined as immediate relatives of U.S. citizens — spouses, parents, and children under 21 — are exempt from the limits. 

The proposed tweaks to the family visa system have become a sticking point for some immigrant advocates, who hope to persuade legislators not to exclude siblings or adult married children over 30. The Senate Judiciary Committee is expected to begin parsing the bill on Thursday.

See the entire Visa Bulletin for May 2013 here.