Insurance giant John Hancock is jettisoning additional office space in Boston, putting another 160,000 square feet of space on the sublease market. It’s making an already bad office market even worse in Boston. How bad? Colliers recently reported the city’s office vacancy rate at about 23 percent. But that’s the official rate. The unofficial vacancy rate includes what’s called the “shadow” market, i.e. space that’s technically leased to a tenant but isn’t fully occupied due to remote work, etc. Some think the actual vacancy rate, when “shadow” space is included, is around 40 percent.