Title: Visitors and the ‘hotel problem’
Author: rhinehart
Published: February 16, 2023
Last modified: September 24, 2025

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 1. [User handbook](https://docs.parse.ly/user-handbook/)
 2. [Measuring and reporting performance](https://docs.parse.ly/user-handbook/measuring-reporting-performance/)
 3. [Understanding Parse.ly calculations](https://docs.parse.ly/user-handbook/measuring-reporting-performance/calculations/)
 4. [Visitors](https://docs.parse.ly/user-handbook/measuring-reporting-performance/calculations/visitors/)
 5. Visitors and the ‘hotel problem’

#  Visitors and the ‘hotel problem’

A common mistake in content analytics is improperly adding [visitor](https://docs.parse.ly/measuring-reporting-performance/calculations/visitors/)
totals over a period of time.

Web analysts call this the “[hotel problem](https://en.wikipedia.org/wiki/Web_analytics#The_hotel_problem)“:
You cannot add visitor totals for a range of dates in a period and have that total
equal the actual number of visitors in the period.

For example, summing up visitor totals from Monday, Tuesday, and Wednesday will 
not equal the correct visitor total for the 3 days as a whole. Similarly, adding
visitors from every day in a month will not match the correct total visitors for
the month.

This is called the hotel problem, because it’s often best illustrated with a chart
of hotel guests:

|  | Monday | Tuesday | Wednesday | 
| Guest 1 | x | x |  | 
| Guest 2 |  | x |  | 
| Guest 3 | x | x | x | 
| **Daily visitors** | 2 | 3 | 1 |

Adding the number of hotel visitors from each day above results in 6:

`2 + 3 + 1 = 6`

But from Monday-Wednesday, 3 visitors stayed at the hotel, not 6. You cannot add
the daily totals and get the accurate total for the full date range.

As another example, here are daily visitor totals for a small site tracked by Parse.
ly:

|  | Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday | 
| **Daily site visitors** | 423 | 257 | 181 | 228 | 168 | 166 | 148 |

Adding the site visitors from each day results in a total of 1,571:

`423 + 257 + 181 + 228 + 168 + 166 + 148 = 1571`

But the actual total number of site visitors, when looking at a report for the entire
week, is 1,231. Some visitors came to the site more than once during the week — 
adding the total from each day means you count those return visitors multiple times
instead of once.

**You cannot add visitor numbers from individual dates in a period to get the correct
total**. You must run a report for an entire period to get the correct visitor total,
be it a week, month, quarter, or year.

Last updated: September 24, 2025