Counting People with Mid-Millennium Numbers

Yesterday marked a milestone of sorts. I reached a diurnal age of 26500, a somewhat unremarkable number commemorated with the tweet shown in Figure 1.

Figure 1

I appended two screenshots to the tweet, one from the OEIS (Figure 2) and the other from Numbers Aplenty (Figure 3):

Figure 2

Figure 3

For some reason, I was prompted to think about what the representation of 26500 might be in Roman numerals. It turns out to be as shown in Figure 4.

Figure 4

So what has any of this to do with counting people? Well, nothing really but as I was investigating the number's properties, it occurred to me that this would be a popular rounding number for populations of towns and islands or communities with common interests or characteristics. This can be confirmed from the following data:

• Tick-borne encephalitis, TBE, has been observed in Aland Islands (population 26,500) for more than 60 years (source). Interestingly:

The self-governing province of the Åland Islands lies off the southwest coast of Finland. Åland is an autonomous, demilitarised, Swedish-speaking region of Finland. Åland consists of more than 6,700 islands, but the current population of over 30,000 live on only 60 islands. Source.

• The most recent mid-year population estimates (2020) for the Outer Hebrides gives a population of 26,500. This shows a decrease of 0.8% (220 persons) from mid 2019 to mid 2020. Source. 
  
  
• Unemployment in the first quarter of 2020: Further rise in Gaza’s unemployment rate; 26,500 people lost their jobs even before the pandemic. Source.
  
  
• CDC estimates Salmonella bacteria cause about 1.35 million infections, 26,500 hospitalisations, and 420 deaths in the United States every year. Food is the source for most of these illnesses. Source.
  
  
• On 30 June 2020, the population of Na h-Eileanan Siar was 26,500. This is a decrease of 0.8% from 26,720 in 2019. Over the same period, the population of Scotland increased by 0.0%. Source.

• The Aromanians in Romania are a non-recognised ethnic minority in Romania that numbered around 26,500 people in 2006. Source.
  
  
• At June 2011, there were 1.01 million children under 15 years of age in Victoria, with boys outnumbering girls by 26,500. This age group comprised 18% of the total Victorian population, down from 20% in June 2001. Source.
  
  
• Published estimates of the risk of vaccine-induced thrombotic thrombocytopenia (VITT) from countries with moderate to high data quality range from 1 case per 26,500 to 1 case per 127,300 first doses of AstraZeneca/COVISHIELD administered. Source.
  
  
• The number of dwellings in Camden Council is forecast to grow from 26,500 in 2016 to 79,631 in 2036, with the average household size falling from 3.08 to 3.01 by 2036. Source.
  
  
• Welcome to the official website of Nicholas County -  a safe, rural community located in the heart of central WV.  County Seat - Summersville; Population: 26,500; Home of WV's largest lake  in the county. Source.
  
  
• February 11, 2021 — The number of vaccine doses available for New York City each week received a 26,500-dose boost through a federal program that provides retail pharmacies with the COVID-19 vaccine. Source.
  
  

The list goes on indefinitely. Of course, the same would hold true of other mid-millennium numbers like 25500 and 27500. For example:

The increase in the number of students inside Midland ISD compared to the start of the previous school year will top 1,000. Superintendent Orlando Riddick said Tuesday the district’s student population appears to not only have eclipsed 25,000 but will end up closer to 25,500. September 2017. Source.

So I've coined this special term, mid-millennium numbers, to describe a class of numbers that are commonly used when quantifying data that cannot be precisely determined. These are to be preferred to millennium numbers such as 26,000 which appear a little too "approximate" (having only two significant figures as opposed to the three of 26,500).