What are the material differences, UK visitor visa vs USA visitor visa

It is on stackexchange that I read for the first time that there is a material difference between UK and USA visas. That difference being that while the US visa essentially only gives you permission to travel to the US border at which point you will be evaluated for entry into the USA, the UK visa aka entry clearance is one which already essentially gives you permission to enter the UK and that your interaction with immigration at the airport is mainly a formality.

Coming from a person who was a non visa national who previously had to apply for and was approved many UK and UK visas and visited both countries quite a bit, I find no material difference between the two as suggested. The questions I get at the UK airport from immigration officials is no different in depth from what I got at the US airport. I know anecdotally it is the same with friends of mine and virtually everyone I know personally who has visited both countries. Actually most of those people have asserted that UK airport immigration are tougher in their questioning.

Does anyone have access to data showing the percentage of people(preferably with visas) denied entry at USA borders vs those denied at UK borders to determine if that difference is statistically significant? Information like below would be somewhat helpful extrapolating the data required

My null hypothesis is that there is no significant difference in the proportion of people with visas denied entry to both countries and thus no material difference in the UK and USA visitor visa.

H0: p1 = p2

where

p1 = the proportion of denied entry arrivals for the USA, and

p2 = the proportion of denied entry arrivals for the UK.

This report implies I may be right and that for nationals of some countries, there is no difference.

The results of such a hypothesis test will be another data point in informing my decision whether to go for a UK entry clearance before my next visit.

Disclaimer: I am from a sub-Saharan developing country (as are most of the people I reference) which like most sub Saharan countries has a high incidence of visitors to developed countries not being true visitors, but people looking to emigrate.

To apply some back-of-the-envelope math:

In 2015, there were 15.3 million non-EEA national arrivals to the UK (9.4 million as visitors). That same year, 17,279 people were “refused entry at port and subsequently departed”. There isn’t perfect overlap (surely some of those refused entry were EEA nationals), but that gives a rough refusal rate of 0.1%.

This, of course combines both visa nationals and non-visa nationals, and detailed breakdowns between the two categories are not available without making a public records request, to the best of my knowledge. However, that report does say that 10% (1,813 people) of those refused at port are US citizens and 5% are Brazilian citizens, both countries that do not require visas for visits to the UK. By way of comparison, 29% of non-EEA visitors to the UK are Americans.

In short, very few people, from either country, are refused. This applies to both visa-holders and visa-exempt nationals.

If you need further statistics from the UK authorities, I invite you to make a request under Freedom of Information law at whatdotheyknow.com.

Beyond that, I wouldn’t view this situation as a material difference between US and UK visas, so much as a difference in how these countries view the role of their border agencies.

US Customs and Border Protection’s position is clear: “Issuance of a visa does not guarantee entry to the United States. A visa simply indicates that a U.S. consular officer at an American embassy or consulate has reviewed the application and that officer has determined that the individual is eligible to enter the country for a specific purpose. The CBP Officer at the port-of-entry will conduct an inspection to determine if the individual is eligible for admission under U.S. immigration law.” Indeed, US law includes a presumption of immigrant intent, and a visitor must be prepared to rebut that presumption and convince the officer that he or she plans to return home.

In the UK, with thanks Crazydre and phoog from the comments of a now-deleted answer, entry clearance still has the same black-letter policy: “In all cases, the authority to admit someone to the UK ultimately rests with the Immigration Officer (IO) at the port of entry.” But the Immigration Rules more affirmatively state that the holder of a valid entry clearance may only be refused under an enumerated set of circumstances (e.g. fraud, change of circumstances, certain reasons such as criminal history that would ordinarily be grounds to deny entry clearance in the first place). One of these circumstances is where the “officer deems the exclusion of the person from the United Kingdom to be conducive to the public good,” which is a fairly broad catch-all, but the intent is clearly that the holders of entry clearance are to be given leave unless there is a serious reason not to do so.

In other words, US policy gives more discretion to the officials at the port of entry to determine whether to admit a visa-holder, while the UK rules state that someone with entry clearance is to be given leave to enter unless specified circumstances exist.