Conduct research to trace the polarization of Congress and the number of bills passed each legislative session. Evaluate your findings for any identifiable trends and relationships between the two. Identify any additional factors that could influence the proportion of bills passed each legislative session. Can you draw any relational conclusions with the data you collected?

In the twenty-first century, the United States Congress became much more polarized than in the previous century. The 108th Congress that took over in 2003 marked the last time over 500 laws were enacted during a congressional term. Prior to 1991, it was typical for Congress to pass over 600 laws during a two-year term.
During the 2015–2017 term, Congress passed 329 laws, and in the following term they approached 300, out of over 12,000 pieces of legislation.
Polarization between the two major parties became evident in the term of President George W. Bush, from 2001–2009, on issues that involved bailing out big banks in the financial meltdown and whether or not the United States was justified in attacking Iraq. While the two parties have been unified in increasing military spending, the parties have been divided on how to approach conflicts in the Middle East.
One of the main differences between Democratic and Republican lawmakers has been fiscal policy. Republicans have supported President Donald Trump's corporate tax cuts, whereas Democrats have been more vocal on universal healthcare issues. Republicans have taken the stance that businesses should not be forced to pay for health care, whereas Democrats have tried to set policies on insurance coverage for businesses.
https://www.govtrack.us/congress/bills/statistics

In the middle twentieth century, Republicans and Democrats in Congress frequently voted together, or jumped party lines to align support on different issues. Beginning in the 1990s, however, a stark divergence in cooperative voting began to emerge, and greater party loyalty to entrenched ideological positions began to manifest.
According to the Columbia Law Review, this can be attributed—in part—to the collapse of the parties as regional blocs with ideological diversity to ideological blocs with regional diversity. Beyond the reasons for polarization, however, is its observable effects. Specifically, since 1986, when early signs of polarization began to emerge, the number of bills enacted by Congress has decreased from 687 per year to 262 per year in 2017.
While congressional polarization is at its highest peak since the period prior to the American Civil War, the actual significance of this point may be exaggerated by an unusually high level of political cooperation witnessed in the decades of the early twentieth century. This high level of inter-party cooperation may have skewed perceptions as to what constitutes normality in legislative relationships. The increased polarization, therefore, may simply be a return to a "resting state" that is more customary in plural, parliamentary bodies.
https://columbialawreview.org/content/congressional-polarization-terminal-constitutional-dysfunction-2/

https://www.govtrack.us/congress/bills/statistics

Several different organizations have studied the increasing polarization of Congress over the past few decades.
One important way to research polarization is to look at votes by members of different parties on various bills and rank them from conservative to liberal. A recent study by Pew Research did this, and the study shows that while in the 1970s there was an overlap between the most conservative Democrats and most liberal Republicans in voting patterns, that overlap has vanished. The liberal/conservative axis has observed stricter party lines in more recent decades. You can find that research here:
http://www.pewresearch.org/fact-tank/2014/06/12/polarized-politics-in-congress-began-in-the-1970s-and-has-been-getting-worse-ever-since/
Another way to study partisanship is to look at statistics related to cross-party cooperation, including bills co-sponsored by people from different parties and votes crossing party lines. This approach can be seen in a study published in PLOS One:
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0123507
You can view statistics on the number of bills passed in each session at GovTrack. Another interesting summary can be found here: https://govtracknews.wordpress.com/2011/08/04/kill-bill-how-many-bills-are-there-how-many-are-enacted/
From roughly 2000 to the present, there seems to have been a dramatic increase in partisanship and a slight decline (from 6 percent to 4 percent) in the percentage of bills enacted.
This raw data, however, is not particularly informative. One must also consider whether either party had, at any time, a sufficient majority to pass legislation on its own.