What's interesting is that while the House has seen a steady rise in the ideological gap and a steady decline in the number of laws passed, the Senate has seen a more hiccupy process. Between 1966 and 1982 there was a leveling off of the ideological split between the two sides. At the same time, the number of bills passed also stopped its decline and held steady between 200 to 300. Since 2000, however, the Senate has followed a very similar trajectory to the House -- a bigger partisan split and fewer bills passed. (Worth noting: Many people -- especially on the Republican side -- would argue that less productivity by Congress is a good thing.)
Here's the reality. No one says they like gridlock in Congress. And yet, the sort of people we are electing are becoming more and more ideologically polarized. And less productive. And they are doing so why? Because either (a) that is what the people who they represent want, or (b) that is what they think the people they represent want. Either way, the result is the same. More polarization = gridlock. Want to change that dynamic? Start electing different people.