How often do construction workers use hearing protection?

Construction workers and laborers do use hearing protectors on the job - but not enough!

Answer Extra: 

The use of hearing protection is the exception rather than the rule. A study of construction workers in Washington state showed that construction workers were exposed to 85 dBA or higher in about 70% of their workshifts, yet wore their hearing protectors less than 20% of the time.

On the up side, the study also concluded that, on average, workers achieved more than half of an earplug's published Noise Reduction Rating (NRR), and that most times, this was just enough protection for their application.

source: 
Seixas, Noah and Neitzel, Rick. "Noise Exposure and Hearing Protection Use Among Construction Workers in Washington State," September 2004.