What is the size of the micromobility market in the United States?

Clarification/Scope:

Definition: Micro mobility refers to a range of small light vehicles operating at speeds less than 25kmph and driven by users personally (unlike rickshaws). In this post, I am reducing the scope of the question to the first-hand road usage daily commute bicycle market in the United States of America (USA).

Analysis:

There are two approaches to this question. You can calculate the market size by estimating the number of people who purchase the bicycle or by the total number of bicycles sold in the retail outlets/company-specific stores. I am going with the first approach i.e., (the number of people who purchase the bicycle). So the equation becomes

Total Number of who purchase the bicycle in that specific year  (A)* Average cost of each bicycle (B).

A. To estimate the number of people who purchase the bicycle in a year, we need to first divide the population based on age and come with an approximate percentage of willingness in each category to buy the bicycle.

The total US Population: 320M

Average Life Expectancy: 80 years.

The average cost of each bicycle: $400

I am assuming a uniform distribution i.e., you will have 4M in each category. People in the age group of 0-5 generally don't ride any vehicle. So I am discarding them.  People between 6 - 20 generally are very inclined as you have school children/college freshmen.  So 80% willingness is a reasonable estimate for this category. People in the age group, 21- 40 generally drive cars, but with the increasing health consciousness, 60% willingness is a reasonable estimate.  People in the age group 41-60 are generally old and a lot of them have health issues such as knee pain etc. So, 40% willingness is a reasonable estimate. People in the age group 60-80 generally don't ride them. So I am discarding that category.

The catch:  Most of us don't buy a new bicycle every year as we might have one already and the general life cycle of a bicycle is approximately 5 years. So an average person buys only 4 times in the span of 20 years. To explain further, If a person buys a new one at age 6, he is again gonna buy a new one at age 11. So we should divide the total willingness in the answer by 5.

Calculation: ((60M*80% + 80M*60% + 80M*40%)/5)* $400 =  ~ $10.2 Billion.

Note: We can further categorize the demographics as kids may higher propensity. We can also add sports/mountaineering/trek bicycles and further expand the scope. Any constructive criticism/feedback is appreciated.