It depends. It depends mainly on how users will be locating the data they are interested in.
Numerical Stats in a Row
If the page is repeating the same stats groupings in the same order, then positional memory will be used, and the numbers themselves also cue the reader in to positioning - Best bowling 5/45 has a different form to Economy Rate 1.51 and people will use that cue. When positional memory is being used bold numbers and quiet labels are good. The user is, for example, comparing bowling stats of multiple players.
Header to a Report:
In a written report, and by extension the same in web format, it is usually better to bold the labels in a header:
Project: Project 123
Phase: Phase ABC
Department: Department XYZ
Positional memory within the group is less relied on. The typical activity is not scanning multiple reports to find what phase each one relates to or compare project titles, rather it's having read one report, checking what phase that one report relates to or exactly what the project title was. The scanning is interspersed with a different activity of long duration. Finding the header information at all is the main scanning.
Also a factor for bold labels - Longer lists defeat positional cuing more, and bias towards embolding the labels. So a rule of thumb:
Long lists (>5 items) seen rarely (<10 a month): Bold the label.
Short lists (<5 items) seen frequently (>10 a month): Bold the information