Estimate the number of emails that the city of San Francisco receives.

This is an estimation question

Step 1: Clarify scope

a) Do we need to consider only public email providers or corporate email servers

b) Receipts include replies or just first time receipt of email

c) Specific platform (web, mobile etc.)

d) Is it San Fransisco Bay area or just SF City?

I will assume all platforms, only SF City and public email providers viz. Gmail, yahoo mail, msn etc.

 

Step 2:

Main equation:

# of email accounts in bay area * number of emails replied in an hour  

# of email accounts in bay area = number of people with age group > 10 years * # of email accounts/user

Step 2a

Overall population of SF City-800K, ~15 of population is >10 years.

Population under purview- 680K. Assume each of them have on average 5 email accounts across providers.

Number of email accounts in the SF City =3.4Mn

Step 2b

People receive emails/hr as per the following hypothesis

9pm-7am- 15 emails during the entire duration

7 am- 5 pm - 5 emails/hour

5 pm-9 pm- 2 emails/hr

Thus total number of emails received

3.4 Mn accounts x 15 emails  +  3.4Mn x 5 emails/hr x 10 hours + 3.4 Mn x 2 emails/hr * 4 hours =  248 Mn emails.