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Charting the Trans Atlantic Slave Trade

The importance of tracing back where we came from to know where we are headed.

The Trans-Atlantic Slave Trade dashboard maps out the voyages of the slave trade that disrupted the lives of 12.5M enslaved African people over the course of 400 years. The author, Spencer Baucke, created it to challenge our perspective and understanding of ourselves and society.

Spencer Baucke recently created an interactive dashboard that maps out the tragic voyages of the Trans-Atlantic slave trade. The Atlantic slave trade involved the transportation by slave traders of enslaved African people, mainly to the Americas from the 16th to the 19th centuries. The vast majority of those who were enslaved and transported where people from Central and West Africa, who had been sold by other West Africans to Western European slave traders. A small number of slaves were captured directly by slave traders during coastal raids.

Spencer Baucke is a consultant at Tessellation, a boutique analytics consultancy. He enjoys using data to help up better understand the world in which we live. While vacationing in Portugal, he was inspired to create the Trans-Atlantic dashboard.

It’s an understatement to say that Spencer’s dashboard caught my attention. Enthralled by this visualization for what it meant to me, personally, as both a Black American and data enthusiast, I reached out to him to discuss it. I had so many questions, starting with his motivation, process, and the whole experience on an operational and emotional level. Spencer, a consultant at a boutique analytics consultancy, describes these past two years as a deep-sea exploration of big data. He enjoys using data to help himself and others better understand the world in which we live.

As we walked through the dashboards and compared notes. I discovered details about the slave trade and its reach, that were unknown to me. In looking back, I learned more about myself and America.

Allen Hillery: Hey Spencer! Thanks so much for taking the time to chat with me! This Trans-Atlantic dashboard is amazing. What motivated you to create this data viz?

Spencer Baucke: Thanks so much! Really appreciate it!

Honestly man, I just love telling stories that challenge people’s understanding of themselves, America, and the world. I have a huge amount of privilege being a white man. I don’t want Black Americans in this data viz space feeling like they’re the only ones burdened with telling these stories, so I try to be an ally wherever I can.

In my opinion, there is no experience more American than the Black American experience, which is a common theme woven through my race-specific visualizations. We need to talk about these topics more. I firmly believe that presenting these concepts with data creates not only a starting point for dialogue but makes an argument more convincing.

Allen: Can you explain what you mean by the American experience?

Spencer: There is no group of people more uniquely American than Black Americans. The first enslaved Africans got to the land we know as the United States over 400 years ago, so Black people have been in the United States long before the US was a country and long before the European immigrants in the 18/1900’s. Not only have Black people been here and working on building this country before its existence, but all of the great American propaganda that white folks like to think applies to us like perseverance, pulling ourselves up by the bootstraps, and overcoming difficulty with hard work applies to no demographic more than Black Americans. They are literally living proof of it.

Black American culture today is the direct result of the aftermath of the slave trade, where they were stripped of their original identities. Every other group that immigrated here brought pieces of their cultures with them and those cultures over time assimilated into American traditions. For example, the Irish brought pubs and St. Patty’s Day, Italians brought a custom rich with family dinners (with pasta), the Germans brought decorated Christmas trees and Santa Claus and the English brought their language.

Allen: How long did it take to create the Trans-Atlantic Slave Trade data viz and what was the experience like?

Spencer: The viz took me a couple of months to do. The biggest amount of time was spent geocoding all the different locations. Since the data came from old ship manifests and such, there were a lot of places that didn’t register on today’s maps that I had to go back and research. Although that took me many hours, it was definitely a labor of love.

The whole experience and discovery were surreal. People on my mother’s side of the family-owned slaves in North Carolina. People on my wife’s side of the family were enslaved in NC during that same time. These realizations weighed heavy on me. The weight was palpable. My family and people were complicit if not explicitly involved. This burden made me reflect on a lot of things about this world, race, this country, and whiteness.

Allen: What did you surmise from your reflections?

Spencer: Surmise — is a good word choice. I looked it up to make sure I had the correct meaning. It means to suppose something is true without having the evidence to confirm it. After this experience, I would say that the key to understanding race in this country is in a lot of ways the key to Americans understanding themselves and our history.

Allen: Can you elaborate on this point?

Spencer: Essentially, the race is not real, it’s a social construct. But the effects of race and the long-lasting legacy of race are SO REAL. And because white people see only the outcomes, and not the origin of race and its implications, that it’s so easy to be confused about race in America as a white person.

I think understanding race can really change how people think about this country. A lot of white Americans like to minimize the impact of race or slavery without realizing that the concept of race has played such a vital role in how they view themselves and others. Not to get too philosophical, but the Irish weren’t considered white at one point. Same with Greeks, Italians, and Jews, so really what is whiteness?

Due to overall ignorance towards the racial history of the United States, many people make assumptions under false pretense. Their grandfather worked hard, saved money, built a better life for the family, pursued the “American Dream” from which the ancestors are still thriving from. I am not discounting the work ethic and the sacrifice, here, but what I am saying is their Black counterparts’ grandparents were doing the same things; however, were systematically excluded from obtaining the same results.

The worst part about it, this is not ancient history. This is recent history. My grandma is still alive and kicking. She was born in 1935 in North Carolina. Her grandfather, William Pharr, was born in 1853 before slavery was abolished in the United States.

Walking Through the Visualization

During its 400-year existence, the Trans-Atlantic slave trade was responsible for the disruption of 12.5M lives. The peak happening in the mid-1700s.

Allen: I started walking through the visualization, 12.5M caught my eye immediately. Just so I and the audience understand, the 12.5M represents enslaved people transported, correct?

Spencer: That is correct. But it is important to note that the actual total will never be known as these are best estimates based upon ship manifests and other documentation from hundreds of years ago. This is the best estimate based upon a lot of research from

Allen: This number also includes people who may not have made it to their intended destination? I’m reading 10.7M survived the passage.

Spencer: From my best interpretation of the data, that is correct.

Allen: This number also doesn’t include offspring produced from this population?

Spencer: That’s honestly a great question that I do not know the answer to.

Allen: Given that this institution lasted about 400 years that number can be doubled at the very least?

Spencer: Well these numbers are numbers from ship manifests, and the voyages across the Atlantic generally took a few months, so I think doubled may be an overestimation especially considering a lot of the people taken were men, and conditions for children would probably not have been conducive to survival, especially taking into account infant mortality rates in the world at that time. But to your point, these estimates are probably low.

Portugal Transported The Highest Amount of Enslaved Africans

Looking at the above chart, Portugal transported nearly half of the 12.5M enslaved Africans.

Allen: One thing I found interesting about this chart is the number of people transported by the Portuguese.

Spencer: Yea, Portugal is not necessarily the country that most Americans would associate with the slave trade. If you harken back to middle school history class, Portugal was a huge world power in the 15th and 16th centuries, so they were really one of the early adopters of the slave trade.

Allen: This was a game changer as I always assumed the British started the institution. Based on our discussion, I carried that assumption because The British traded in North America and parts of the Caribbean. Your visualization helps a lot in piecing this all together.

Spencer: That’s right. It’s normal as an American to think of the British when talking about slavery because they were the ones who settled this part of the continent at that time. That’s also why we speak English.

Allen: Six African countries to date have Portuguese as their official language. Including Angola, Mozambique, Guinea-Bissau, Cape Verde, Sao Tome and Principe and Equatorial Guinea.

Spencer: Brazil also speaks Portuguese because that’s where a vast majority of enslaved people being transported by Portuguese ships ended up. If you think about all of the countries around the world that speak European languages, it is a safe assumption that the slave trade and colonization were involved.

Voyages Originating From Lisbon

Voyages originating from Lisbon accounted for enslaved Africans being taken from Western and Central Africa to Brazil and parts of the Caribbean.

Allen: You mentioned earlier a recent visit to Lisbon inspired this data viz? Tell us more about that.

Spencer: It did. I visited Lisbon with my wife and we went on this walking tour that taught us about a huge earthquake that destroyed a large part of the city in 1755. When describing how the city was rebuilt, our tour guide mentioned that they used money and resources from their “investments” in Brazil. In essence, the free labor of black people toiling in the sugarcane fields of Brazil paid for Lisbon to be rebuilt. I started wondering about these slave-owning European countries with glorious monuments and statues, wealth and resources… is this how they paid for those as well?

Allen: This reminds me of the reparations Georgetown University has been making to the descendants of slaves who built their prestigious institution for free. It started with them giving the descendants of the 272 enslaved Africans preferred admissions. When you connect all the dots and realize how for decades, only white males were able to attend these universities — It’s disheartening. It also goes back to the point you were making earlier about not understanding race in America and how we got here.

Spencer: Now these monuments and opulent city squares draw huge amounts of tourists that fund their economy. It’s easy to think that these cycles of outcomes we see today were set in motion hundreds of years ago by the slave trade.

Voyages Originating from Liverpool

Voyages originating in Liverpool accounted for enslaved Africans being taken from Western and Central Africa to the Caribbean and American colonies. One interesting fact that came up was that only 600K enslaved Africans were brought to North America representing 5% of the total transported.

Allen: So looking at the visualization, when you begin to hover and select the starting point for the voyage, some of the circles are larger. For example, Liverpool was larger than London. What does that signify?

Spencer: The size of the circles on the locations signifies the number of people that had voyages either start, stop, or end at that location. Each of the circles represents a location, not necessarily an individual voyage. I tried to aggregate the voyages by location to see the bigger picture.

Allen: I noticed the British voyages didn’t have a relatively large amount of slaves disembarking in the States?

Spencer: Comparatively, yes that’s an accurate interpretation. One of the stats that shocked me was that about 600,000 enslaved people were brought to North America out of the 12.5M, which is about 5% of the total. A vast majority of enslaved people ended up in the Caribbean and South America.

Allen: I saw a large number of slaves being dropped off from the Liverpool voyage. Is that the case?

Spencer: As far as Liverpool goes, yes, a HUGE amount of slave trade voyages originated from this port. It is estimated that about 1.5M people were transported on ships coming out of Liverpool.

Allen: You cited as your data source. How thorough was their data in helping you put this together?

Spencer: Their data was as thorough a data set out there I think. They’ve obviously put a ton of effort into curating their data.

Allen: What other data points are available that you didn’t use in this visualization. Can someone find the names of ships, captains or enslaved passengers?

Spencer: You can see ship names, captain names, flags that the ships flew under, voyage dates, and much more. The data that I was looking at was at the voyage level, so there were no passenger names, although I doubt that the names of the people transported would have been more than a number.

Allen: What would you recommend for someone like me who might be interested in tracing their roots or understanding their past. Would your data viz and the underlying data set be a good start?

Spencer: I think that looking at data like this might not be able to help you definitively trace your roots, but it could definitely give you some clues as to what regions your ancestors may have come from.

Allen: What were your goals in creating this data viz? Do you think you achieved them?

Spencer: My goal when creating data visualizations is to get people thinking deeper about basic assumptions they make about themselves and the world. I think the people that will end up looking through my viz and taking the time to think about the topic aren’t the ones that necessarily need to be doing it if you know what I mean. But hey, I feel like if I can get one person to think more about these topics I feel like it was worth it.

Allen: What is your next visualization subject going to be?

Honestly, I am taking a break from data viz for a little bit. I got really burnt out last year and tried to do too much especially since I had a new job that included lots of travel away from home and we had a very young child to boot. If I do get around to doing something for fun again I’ll make sure to let you know.


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