...And its increase.
First, let's examine the trends usually cited for this. Changes in communication technology have made it a lot quicker to reach people. Changes in transportation technology have made it quicker to go long distances. And recent changes in computing have made mobile devices a thing - not only is communication faster, but also always accessible, as are games, TV, calculators, and cameras.
Now, has society changed a lot over the last hundred years? Of course. Can you now chat with someone on a different continent in seconds, rather than weeks or never? Sure. Can you fly to meet them in under a day? If you have the money. And don't people spend all their time staring at screens nowadays, instead of more wholesome activities? Some do.
But here's where I start disagreeing with most commentators on this topic: when they follow all the above with "Isn't society so much worse now, and people so much more stupid, frazzled, and sheep-like?" Usually it's phrased as the corollary: "Weren't people nicer, more relaxed, and independent back in [an idyllic period of the commentator's youth, or favorite romanticized historical era]?" My thesis here is that this is just plain silly.
People are who they are. You may think you are anonymous on the internet, but you are still you. Cut yourself off from technology and time would still be passing at the same rate, your thoughts would still be going through your brain at the same speed, and you'll still have all the same vices and virtues. Your mom will still love you, your boss will still want things yesterday, and you'll still have that strange desire to put captions on pictures of your cats.
So I'll grant you that things are in one sense faster now. But I'd pick a different set of scapegoats for societal ills... and I'll give you a hint, they're the same ones they used to be. Family ignoring each other around the dinner table? I have a feeling they would have been doing the same a hundred or thousand years ago. I mentioned vices and virtues earlier... I'd wager good money that people were just as likely then as now to be greedy, generous, lustful, loving, violent, nice, prejudiced, or compassionate. These translate into how we treat those around us, regardless of whether it's taking place online or off.
