For a state to create a new law, a bill proposing the idea must be introduced by a legislator. The idea may or may not have originated with that particular legislator, but the legislator will need to officially “sponsor” it. A bill can have just one sponsor, or multiple sponsors. Intuitively you would expect more sponsors would increase the chance of passing. I was curious if that was true. Does a bill with more sponsors have a higher chance of passing? And, since we’re looking at it, does a legislator who sponsors more bills have a higher chance of success?
The map below shows how many sponsors a bill has, on average, in each state. (The map is made with OpenHeatMap and isn’t https, so you might need to click on the shield in your browser bar to let the map draw. Notice also you can zoom in to see the smaller states.)
The average varies from just a handful of bills in most states, to 20 average sponsors per bill in Pennsylvania, and a whopping 29 in South Carolina, which seems to view bill sponsorship as a team sport. You might wonder if perhaps South Carolina has an exceptional number of legislators. Here’s the basic picture:
Legislators by State
* this map was made a few years ago and numbers may have shifted a bit since then mostly because of the occasional open seat, but the general comparison between states still holds
So yes, South Carolina has a relatively large number of legislators. But certainly not the most, New Hampshire is the far away winner, but South Carolina is in third place. Which mean New Hampshire is probably the biggest outlier, with 494 legislators, but an average of only 5 sponsors per bill. So does South Carolina’s high rate of sponsorship result in a high rate of passing bills?
This post from 2012 and this one from 2015 look in depth at passing efficiency by state. But for our purposes let’s use this summary map showing which states have the highest percentage of bills passed (darker is higher, with Idaho around 60% and New York around 3%, again more detail available in the above posts):
You can see South Dakota has a relatively large average number of sponsors per bill, and a high rate of passing bills. Michigan does moderately well. But Pennsylvania and South Carolina look like they actually pass fewer bills than average. Is there partisanship at play? See this post to explore that question (spoiler alert: maybe a little).
Without regard to what state a bill is from, more sponsors is strongly correlated to a higher chance of passing, at least up to 100 sponsors. Above 100 sponsors we have a smaller sample size. Whereas we have 640 bills with 40 sponsors, but only 33 bills with 135 sponsors, for example. There’s good reasons for that; not every state even has 100 legislators, and how often will everyone sign on to one single idea? But where we have lots of data we see an extraordinarily close correlation. From 1 to 80 sponsors your chances of your bill passing rise steadily from 20% to 40%.
So although more sponsors for a particular bill increases its chance of passing, states with a culture or tradition of having a lot of sponsors per bill don’t necessarily pass more bills overall. However, within SC, the correlation still holds, but not quite as strongly:
What about our second question? How many bills, on average, does a legislator sponsor? Turns out the states vary an enormous amount:
The Mountain West and Great Plains tend to have an average of 10 to 20 bills per legislator. Not surprisingly, with all the sponsoring going on, South Carolina’s legislators have a high average number of bills sponsored by each legislator – 610! The relevant additional question here is how many bills are introduced in each state. Here’s a recent snapshot:
So New York has a huge number of bills in general, so pretty much legislators would have to be sponsoring a lot of bills, just to get that many bills introduced. South Carolina and Pennsylvania do have a slightly larger than average number of bills, but not enough to say that’s why their legislators are sponsoring so many bills. There we have to look back at the high average number of sponsors per bill; lots of legislators are signing on to each bill.
What I do see, comparing this map to the map of the percentage of bills passed, is that largely the fewer bills a legislator writes, the higher a percentage of bills gets passed. Here is a look at those two variables together on a scatter chart, ordered by percentage passed (US stands for Congress)
Although the correlation isn’t perfect, there’s a definite trend that the states with a larger number of average bills sponsored by each legislator tends to result in a lower percentage of bills passed. From this point of view, although South Carolina legislators seem to be most collaborative, they pass a lower percentage of their bills than 30 other states. Tennessee legislators are arguably most impactful, sponsoring a relatively large number of bills, with a relatively high percentage passed. Of course this may partially be because of how many resolutions Tennessee tends to have in each session.
So, overall, a bill with a lot of sponsors is more likely to pass. And the more bills a person sponsors, the lower their percentage of bills passed will be. Which is a bit paradoxical. To maximize your pass ratio, you should be focused and only sponsor a few bills, choosing only the best ideas and giving them lots of effort. But you should convince as many of your colleagues as possible to be less focused and sign on to your bill. The reality of passing legislation is, of course, more complex than that. But that central tension is real, at least according to the numbers.
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