A benefit of easy access to computation and publication tools is that public figures can be more easily made accountable to their performance, whatever their domain of endeavor, and then have their status affected appropriately. Of course not just primates but many social animals track past behavior and reciprocation albeit sloppily, and we humans started doing this more rigorously by applying integers to one measure of exchangeable liquid utility in the Middle East fifty centuries or so ago (money). But there were often ways to opacify performance and game the system. I am optimistic that technology means this is changing for the better. Impressively, after this U.S. election cycle, even Dick Morris had to explain himself on FOX.
So why don't we measure and track legislators, in terms of the effectiveness of the laws they write?
It would be nice to hear people in bars talking about averages for legislators or entire Congresses instead of yards rushing. "Remember that 114th Congress? They had a term average of point eight nine. Those were the glory days. Not like these bums now, they haven't been above point seven oh any single week."
The first thing that's terrifying to contemplate about the legislative process is that the feedback loop (between writing good bills and re-election of the writer) is not just broken, it basically never existed. Imagine if a company were run like this! Think about it: one or a few legislators (out of 435 in the House) write a bill, in committee, invariably with lobbyists "advising" them. The bill goes to the floor for a vote, which in the U.S. at least will usually be along party lines regardless of the bill's content. And voters do not reward or punish the legislators who wrote the bill - because voters ignore bills (whether they were good or bad) and decide who to vote for based on what tribal loyalty noises the politician makes during the election, and whether jobs were gained or lost during the last term, which usually has nothing to do with anything the legislator did. Occasionally a bill will become known for its extreme unpopularity, and for this reason there's every reason to avoid association with laws passed, and few reasons to be associated with them in the minds of voters. In very rare cases, a bill later becomes very popular, in which case at election time it was their idea all along, and we see five hundred thirty-some gruesome examples of the free rider problem.
It is truly amazing any law ever gets passed.
(On the complexity of modern government in general and how this breaks the feedback loop, see Steven Teles on "kludgeocracy": "[it is] hard for Americans to attribute responsibility when things go wrong, thus leading blame to be spread over government in general, rather than affixed precisely, where such blame could do some good. The consequence of complexity, then, is diffuse cynicism, which is the opposite of the habit needed for good democratic citizenship...The complexity that makes so much of American public policy vexing and wasteful for ordinary citizens and governments, however, is also what makes it so easy for organized interests to profit off the state's largesse." Additional emphasis by Salam here.)
This is a problem in medicine, where it's hard to think of a way to put one number on a physician that measures their performance. Consequently, we use the burdernsome approach of looking individually at every condition they see and procedure they do, and compare them to national averages. In legislation the problem is worse, because laws are (in theory) solutions to problems that are not just unique but only recently appeared, which is why they now require laws.
A related question to problem #2 is that legislator effectiveness should not be measured just by number of laws produced. The number of laws sponsored or co-sponsored is in large point dependent on the legislators' committee seats and seniority; and beyond that, just because someone is producing lots of laws, doesn't mean those are good laws. In fact part of the measure of legislator effectiveness could be how many laws (and regulations!) they retire, or subsume within new laws. (A constitution and legal system written in a consistent programming language, requiring the full set of laws to be compiled every time the session ended, would be one way to decrease redundancy and legislative sclerosis.) It may be appropriate that in a more complex time, we have more laws than we did a hundred years ago, but resignation to this type of legal sediment accumulation is unlikely to produce an optimal government.
One solution to the difficulty of how to measure individual laws would be not allowing a bill unless legislators made a concrete prediction about its effect - and then tracking whether they were right. The legislators' effectiveness would be some combination of their accuracy, and their effect on a concrete metric - money, jobs, happiness in their district, etc. No one cares that you were 10 for 10 on declarations that the sun would keep rising in the east, but if you miss a few while increasing quality of life years in your district, maybe you're a keeper. This of course is a version of futarchy, applied to legislators. It might actually be easier to install it in a legislature first, before it's installed among the general electorate, since many people are likely to recoil at the suggestion that voting be counted differently for different people for any reason. But sticking it to Congress, well now you have something!