According to the January 2011 visa bulletin, the U.S. Department of State was issuing immigrant visas (or green cards) to siblings of U.S. citizen who filed a petition on or before January 1, 2002. However, the March 2011 visa bulletin indicates that there has been a retrogression and immigrant visas to siblings to U.S. citizens are being issued for petitions filed on or before January 1, 2000. This means there has been a halt to issuance of immigrant visas in the 4th preference category-siblings of U.S. citizens.In general, there are only 65,000 visas available for siblings of U.S. citizens. If this retrogression is an indication that all 65,000 have been exhausted, then new visas will be available on October 1, 2011. This is unwanted news for siblings of U.S. citizen who have applied for adjustment of status or have their petitions pending at the Embassy. The fiscal year for issuance of immigrant visas is Oct. 1st to Sept. 30th.What is visa retrogression?Sometimes, a priority date that is current one month will not be current the next month. This is called visa retrogression, which occurs when more people apply for a visa in a particular category than there are visas available for that month. Visa retrogression most often occurs when the annual limit has been reached. When the new fiscal year begins on October 1, a new supply of visa numbers is available and usually, but not always, brings back the dates to where they were before retrogression