How many people aged 13-24 purchase online clothing in London, New York City, and Los Angeles?

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How many people aged 13-24 purchase online clothing in London, New York City, and Los Angeles?

While there is no pre-existing information to fully answer your question, we've used the available data to pull together key findings. We have triangulated, based on the data and assumptions detailed below, that there are approximately 1 million New Yorkers age 13-24 who collectively spent $249 million in online clothing purchases in 2017 and another 1.5 million Los Angeleans of the same age who collectively spent about $374 million, averaging $249 each. We further triangulated that 693,000 Londoners age 13-24 purchased clothing online in 2017. Due to a lack of public data, we cannot determine the total amount spent by this age group.
Below you'll find an outline of our research methodology to better understand why the information requested is publicly unavailable, as well as a deep dive into our findings.
METHODOLOGY
We started by searching for demographic information about the e-commerce market from trusted sources. While this provided some information that ultimately informed our triangulation as noted below, we were unable to locate a source that provided segmentation by age, industry, and location. After an extensive search, we were unable to pin down any statistical information about e-commerce by city. The US Census Bureau, for example, does not provide a breakdown by demographic, industry, or state (let alone by city), nor did Pew Research or Bold Metrics. Based on this, we determined that this information has not been publicly published.
We considered using Google Trends to provide a general idea as to the relative use of search terms related to online shopping in different states (e.g., "Amazon" and "clothing" together). However, it came to our attention that 69% of online clothing shoppers purchase 76-100% of their clothing from larger national/regional retailers. Given the sheer number of clothing retailers and their uneven distribution across the US, we deemed that this would not provide sufficient accuracy. This is especially true since Google Trends does not provide true counts of searches, let alone conversions of sales (versus, for example, comparison shopping while in-store).
However, as we will show below, we did discover enough information in our search to at least triangulate a rough estimate on the number of online shoppers in the requested demographic.
USEFUL FINDINGS: LONDON
According to Statista, 73% of people aged 16-24 had purchased clothing online in 2017, compared to 63% of the general population. We could locate no information for purchasers below the age of 16. The US data (see below) shows that those below age 17 are half as likely to do most of their shopping online as the 18-24 age bracket, so for the sake of triangulation, we will assume that this holds true in the UK as well and that only 36% of those age 13-15 had purchased clothing online.
TRIANGULATION: TOTAL ONLINE CLOTHING CUSTOMERS IN LONDON
Greater London has a population of about 7.2 million, of which 6% are aged 10-14, 6% of which are aged 15-19 and 6% of which are aged 20-24, or approximately 432,000 for each age bracket. This means that 73%, or about 631,000 Londoners age 15-24, had purchased clothing online in 2017. Assuming an even distribution (6% / 5 [14-10] x 2 [ages 13 and 14]), 2.4% are ages 13-14, or about 173,000. If 36% had made clothing purchases online, this would come to another 62,000 individuals.
We, therefore, estimate that about 693,000 (631,000 + 62,000) Londoners age 13-24 have purchased clothing online in 2017.
USEFUL FINDINGS: NEW YORK CITY AND LOS ANGELES
Since we are unable to locate a breakdown of the e-commerce clothing market by state, we will first establish the size of the US market in general before narrowing the field down to New York and Los Angeles.
Overall, 43% of US shoppers bought clothing, shoes, and accessories online in 2017. Another source states 47%, in comparison to 63% of UK shoppers. This illustrates that all available sources are providing estimates only, often using survey data, and not true numbers derived directly from the sales data itself. For our purposes, we will use the 43%, as that figure comes with some additional demographic information: 67% of Millennial purchases (defined as those age 18-34 in 2015, and so 20-36 in 2017) are made online, compared to an average of 42% for Gen X (56%), Baby Boomers (41%), and Seniors (28%) combined. This suggests that Millennials make their purchases online 1.6 times (67 / 42) more often as other generations.
Some additional statistics include: In 2016, 5.8% of those age 14-17 and 12.9% of those age 18-24 were predominantly online shoppers (not limited to clothing). A small number (7%) of people in the US who are age 18 to 29 state that they always purchase their clothes online, and another 21% claim to shop online for their clothes very frequently.
Unfortunately, the available sources do not offer either information about Generation Z (those up to 19 years of age) or Millennial habits as they specifically pertain to clothes. However, we can derive some back-of-the-envelope calculations.
If Millennials are truly 1.6 times more likely to make purchases online than other generations (see above) and 43% of the US population purchases clothing online, then we may estimate that 69% of Millennials (43 x 1.6) have made purchases online. However, we know that only about half as many below age 18 are predominantly online shoppers (5.8% to 12.9%). For the sake of estimating, we will take that to be true of the percentage who ordered clothing online in 2017, or about 34% (rounding down).
TRIANGULATION: TOTAL ONLINE CLOTHING CUSTOMERS IN LOS ANGELES
In terms of population, Los Angeles has about 13.3 million people. 6.92% are age 10-14 and so, using the same calculation as for London (6.92% / 5 [14-10] x 2 [ages 13 and 14]) we estimate that about 2.8% are ages 13 and 14, or about 372,000 (2.8% x 13.3 million). Another 15% are ages 15-24, so nearly 2 million (15% x 13.3 million) fall into this age bracket. Based on the above, we estimate that 69% of those 2 million and 34% of the 372,000 purchased clothing online in 2017 for a total of approximately 1.5 million.
TRIANGULATION: TOTAL ONLINE CLOTHING CUSTOMERS IN NEW YORK
As of July 2015, New York City's population was approximately 8.5 million, of which an estimated 2 million were under the age of 18. New York currently has about 616,000 children age 10-14, which comes to about (616k / 5 x 2) 246,000 age 13-14. It has another 1.3 million individuals age 15-24. Again based on our above findings, we estimate that 69% of the 1.3 million and 34% of the 246,000 have purchased clothing online, for a total of a little under 1 million individuals.
HOW MUCH IS SPENT ONLINE
While we were able to determine that the average British shopper spends £1042 ($1464) per year on clothing, after an extensive search, we could not determine how much of this is spent online, nor whether the amount spent in London is higher than the country average. Consequently, we are unable to provide online clothing purchase totals for the UK.
We were able to triangulate a bit more in the case of the US, but with two assumptions: First, that the amount spent in an online purchase is independent of the person's location. This seems logical and defensible. The second is that the average amount spent is independent of the person's age. Quite obviously, this isn't true, but since we are unable to find a public source that breaks down average expenditures by age, we will utilize this assumption to provide an estimate.
In 2017, there were a total of $81 billion online fashion and apparel purchases in the US. The total US population in 2017 was about 325 million. Therefore, the 1 million New Yorkers aged 13-24 who purchased clothing online in 2017 would have spent (81bn x (1 / 325)) a total of about $249 million, or about $249 each. The 1.5 million Los Angeleans would have spent about $374 million (249 x 1.5), again about $249 each.
CONCLUSION
We triangulate that there are about 1 million New Yorkers age 13-24 who collectively spent $249 million in online clothing purchases in 2017 and another 1.5 million Los Angeleans of the same age who collectively spent about $374 million. This averages to $249 each. We further triangulate that 693,000 Londoners age 13-24 purchased clothing online in 2017, but due to a lack of data cannot determine the total amount spent by this age group.

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