I'm not sure where you get the 60% number. I know Wikipedia states it, but the reference they provide does not support that number. It actually says that 45% of British Indians are Punjabi, which is still a large number, but not so large.

I think one reason for the over-representation of Punjab is because of the Sikh population. While both Hindu and Sikh Punjabis have emigrated to the UK, 65% of British Indians of Punjabi origin are Sikh, and 35% mostly Hindu (with around 1% Christians and Muslims mixed in). If not for the Sikh diaspora, probably Gujaratis would be the biggest Indian community in the UK.

This is not unique to the UK, although it does have the largest Sikh population outside India. Many other countries also have a very high proportion of Punjabi Sikhs, for example around 30% of Indian workers in Gulf countries, around 20% of Indian immigrants in Canada.

I can think of a couple of reasons why this may be so. One is that in Hinduism, there was a taboo against sea voyages, referred to as "kala pani" (literally black water). The taboo is called samudrolanghan, and you risk losing your varna or caste status if you cross the sea. There were several reasons for this, for example, it meant being away from family and your own kind of people, it was hard to conform to Hindu traditions and Hindu dietary norms living among strangers, and you were far from the waters of the Ganges.

This was originally only a requirement for Brahmins, but later other castes also developed similar beliefs in their desire to emulate the Brahmins. In fact, when the British wanted to transport Indian laborers to places like South Africa or the Caribbean to work the farms, they found strong resistance among Indians because of crossing kala pani. The British employed several stratagems to overcome this reluctance, including supplying their ships with tanks of water from the Ganges, and providing Ganges water periodically to Indians living abroad in these places.

Sikhs do not have this taboo, which may be one reason why they emigrated in large numbers to many countries, including the UK. So another way to look at it is from the perspective that it's not so much that there are so many Punjabi Sikhs abroad, but rather that there is a shortage of Hindus, which makes Punjab over-represented among Indian diaspora.

This is evident if you consider the number of Indians compared to other south Asian countries in the UK. There are only 45% more Indians than Pakistanis in the UK, though the India's population is 7 times larger than Pakistan's. The numbers are similar if you consider Bangladeshis. So as a matter of fact, Indians are greatly under-represented in the UK and most countries in proportion to their population. If all Indians emigrated at the same rate as Sikhs, this would not be the case. Hindu reluctance to emigrate has held the numbers down, though this is slowly changing.

Another reason is education and opportunity. The bulk of Punjabi emigration was soon after independence, in the 50' and 60's. At the time, Punjab was the richest state in India (being part of the Indian breadbasket), and it still is among the richest. As a result, Punjabis were among the healthier, better educated Indians at the time. In much of India, those were times of famine due to chronic failure of the monsoons, and the condition of the people was pretty miserable.

Britain was rebuilding after the war, and needed a lot of labor. At the time, they allowed skilled and unskilled workers from all the commonwealth countries, and this is how Punjabis emigrated. I think it takes a certain amount of awareness of the outside world which comes from education, and some self-confidence which comes from being in reasonably good health, to have the chance to emigrate. These conditions were right in Punjab (and Gujarat), but not so great in poorer states. This may be another reason why Punjabi diaspora is so numerous.

I would like to politely reject /u/evanrwt's point about "kala pani" and expand on the latter points s/he makes. It was, if anything, a marginal consideration for the average Indian. The suggestion of vague Sanskrit scriptural verses playing a major role in broad patterns of Indian immigration reeks of Orientalist thinking. Clearly kala pani didn't stop the Hindu majority Gujaratis from dominating the Indian diaspora historically and presently across colonial British Africa, South America (i.e. Guyana), and the Caribbean.

I would argue Punjabis' disproportionate presence in Britain in particular is more rooted in developments during the colonial period. After the 1857 Sepoy Rebellion, the British Indian state made serious overtures to bring Sikhs and other large and powerful Indian ethnic groups "into the fold" so to speak and make them a part of empire. They had naturally realized that a company running a subcontinent wasn't the best way to create a longlasting political entity.

Sikhs among others were labelled as a "martial race" and accordingly were generously recruited into the British Indian Army. Special Sikh battalions were formed and the notion of this turban wearing, manly beard bearing Sikh warrior was given a new, imperial spin. These battalions were well provisioned and trusted by British officials.

This leads to major ramifications relevant to your question.

The first is what was done with retired Sikh/Punjabi soldiers. The land of Punjab means land of five rivers. The British government embarked on an ambitious plan of linking the rivers with various canal irrigation projects to make the region more productive and therefore increase tax revenues and further cultivate resources the empire desired (e.g. wheat, which could be sent to regions like Berar so they could focus on cash crops like cotton). I'm a tad murky on the details of the mechanics of how these agricultural lands were the 'property' of the British Raj to give out, but retiree Sikh/Punjabi soldiers of the British Indian Army were given generous concessions of rich farm land.

Naturally this meant a great success for the British post-1857- they successfully created a militarized and landed group of very pro-British elites. A great example of this proliferation of Anglophilia is Punjab's strong culture of alcohol consumption relative to other Indian states, and the state's high consumption of liquors that are popular in Britain, like whisky and Scotch.

The second point is Punjab's relative affluence. Due in great part to the processes I just described, Punjab was and still is India's agricultural keystone. It was well positioned to take advantage of the Green Revolution.

The point here is that Punjab in particular has a long history of intimate links to the British, Britain, and British institutions. Sikh soldiers played a major role in Britain's fight in WWI and WWII; they had significant and institutional exposure to British culture and practices through their institutional links to Britain (e.g. Sikh specific army battalions).

Exposure and links to Britain/British culture/British people and the means to make an expensive journey across the world and have the means to have the pre requisite educational background (e.g. English skills) the trip necessitated are why Punjabis I would argue developed such a predilection for immigration.

As well as the reasons mentioned by EvanRWT one has to consider the impact of partition as a push factor. People dislocated from their ancestral homes in Pakistan to Bombay or Delhi (on from ancestral homes in the Republic of India to Islamabad or Lahore) would clearly be more willing to move abroad than people in intact ancient communities.

The English were less prejudiced against Punjabis (especially Sikh and Muslim Jaats) than against many other Indians and recruited people from the Punjab (especially Jaats) to work on large building projects post the second world war. Heathrow airport is the usual example , but no doubt there are others.