For me it's less that a fraction would be better and more that it it's not crystal clear what it is 3 times less than, although "3 times less" is something I've rarely heard and may be a US thing. A suitable alternative would be "Appear 33% of the time an average snippet would appear" if fractions are weird, but your point about Americans being our target userbase of 3 is good enough that 1/3rd is fine too.

So for the text, let's use something like this:

```python
SNIPPET_WEIGHTS = ((33, 'Appear 1/3rd as often as an average snippet'),
                   (50, 'Appear half as often as an average snippet'),
                   (66, 'Appear 2/3rds as often as an average snippet'),
                   (100, 'Appear as often as an average snippet'),
                   (150, 'Appear 1.5 times as often as an average snippet'),
                   (200, 'Appear twice as often as an average snippet'),
                   (300, 'Appear three times as often as an average snippet'))
```