A trend which surely had nothing to do with the tech/biotech boom in the area. When a region gains hundreds of thousands of new jobs and doesn't build housing to compensate, then rents are going to increase
There have literally been hundreds of thousands of new jobs created in the region in recent decades. Cambridge alone added nearly 50,000 new jobs since 1980!
So yes 2400 units is a start, but we need dozens more like it before we start to even come close to solving the shortage.
Of course Cambridge didn't add significantly more people than it added housing units. People aren't going to move to the city for a job only to live in a tent down by the railroad tracks!
Instead what happened is that new residents came to the city for high paying jobs and bid up the prices for local apartments. Basically a cruel game of musical chairs where low-income households were forced from their homes and into cheaper neighborhoods in the surrounding cities. (Those poor neighborhoods actually did grow in population faster than housing: people were forced to pack into overcrowded living conditions)
If you're curious about the numbers, over the last 40 years Cambridge added about one housing unit for every four new jobs
The thing with boston/Cambridge is that in addition to “great” companies there are also several top notch universities there so the competition for apartments is even greater.