I understand your point (telecommuting has major effects on office space usage) but it will still be a function of white collar workers in the economy, simply b

I understand your point (telecommuting has major effects on office space usage) but it will still be a function of white collar workers in the economy, simply because a certain percentage of white collar workers will be working in offices for the time to come (although this percentage will change over time). Office space usage will be a function (but not equal to) the number of white collar workers. There might be other variables too.