While B visas are not F1 (i.e., student) visas, a look at issuance statistics since 2006 reveals a positive trend for Vietnamese traveling to the U.S. on business or on holiday. (B-1 visas are for tourism, pleasure or visiting, while B-2 visas are a combination of both purposes.)
In Fiscal Year (FY) 2013 20.3% of all B1/B2 visa applications in Vietnam were refused (PDF download), the lowest percentage ever. This means that about 80% were approved, which is on par with the worldwide average for FY 2012 and places Vietnam in the same league as countries like Ireland (16.9%), Latvia (20.4%), Maldives (22.9%) and Singapore (25%).
This graph illustrates some ups and downs and then a steady decline in the refusal rate starting in 2010.
In FY 2012 the worldwide issuance rate (PDF download) for student (F-1) visas was 74%. Below are two graphs that show significant increases for both B and F1 visas from 2007-2012.
While this information is not released in Vietnam, my guess is that the student visa issuance rate, which has on the rise in recent years, is in the 60-65% range. (Dear Reader – If you have an exact figure, please let me know and I’ll post it, with or without attribution.) It could be considerably higher if students 1) were more familiar with the process and better prepared for the visa interview; 2) did not use the F-1 as an obvious means of emigration; and 3) did not engage in various types of visa fraud.
Another variable, given the latitude that consular officers have and the lack of accountability in the system, is that they sometimes make mistakes often based on false “intuition.” (To err is human, right?) This lack of accountability has also resulted in intentional mistakes, i.e., a number of cases of visa fraud worldwide, including a high-profile one in Vietnam involving Michael Sestak, the former Nonimmigrant Visa Section Chief at the U.S. Consulate General in Ho Chi Minh City.