Labor intensity is the relative proportion of labor (compared to capital) used in a process. Its inverse is capital intensity.
relation
According to many well documented sources (to be cited by others, hopefully), labour intensity, in the above sense, has been declining since the onset of the industrial revolution in late 1700s. Its inverse, capital intensity, has increased near exponentially since the latter half of the 20th century as shown by the chart presented at
References
Labor intensity Wikipedia(Text) CC BY-SA