My usual rule is that it's a bit of a mug's game trying to identify in advance which bill announced in a Queen's Speech will trigger backbench rebellions. Even when you know what's actually in the bill - and in many cases at the moment all we've got is a title - it's difficult to work out which will cause trouble and which will sail through. Too much depends on how the bill is handled - the extent to which the government is willing to give way or concede - and on the context in which any votes take place.  

But when you've got government backbenchers rebelling in almost half of all divisions - our recent research showed that they've been rebelling in 44% of all votes in the last session, a historically unprecedented rate - then it becomes a bit easier. Of the 15 new bills announced yesterday, I'd be surprised if at least 13 don't see some backbench dissent. Unless there is a climbdown, the House of Lords Reform Bill will be the most difficult, but there are plenty of other bills with the potential to cause trouble.

One reason why dissent is so widespread is that it has been coming from both wings of the coalition and on different types of issues. Just over seven in ten (71%) of Lib Dem rebellions in the last session were on social policy (broadly defined), such as the various increases and extensions in VAT, the introduction of free schools and the expansion of academies, and curbs to legal aid and superannuation for civil servants. But nearly half (49%) of Conservative rebellions are on constitutional policy (broadly defined), such as the bills relating to the introduction of AV and fixed-term parliaments. Of this last category, a big chunk (nearly one in five of all Conservative rebellions) has been on Europe (18%), rebellions which are more than double the average size of all Conservative rebellions.

This explains why the two wings of the coalition rarely rebel at the same time. Almost half of rebellions (46%) in the last session saw Conservative MPs rebel alone; just over a third (36%) saw Lib Dem MPs rebel alone. That leaves less than one in five which have seen a rebellion by both Lib Dem and Conservative MPs.

This has important consequences for the likelihood of any government defeat. Even if you take taking the government's paper majority as your guide (and its de facto majority is even higher), then it would take 39 coalition MPs to rebel to defeat the government, but only if the Labour frontbench was to vote with the rebels. There are plenty of issues on which 39 Conservative MPs might rebel, but there are fewer on which the Labour party would be willing to join them. Overall in the last session, 21% of coalition rebellions occurred when Labour was not voting against the government and when there was therefore no chance of a defeat. But that figure rose to 31% of Conservative rebellions.

The hurdles in overturning a large in-built coalition majority are even more acute for the Liberal Democrats. Lib Dem rebellions were more likely to take place when Labour was opposing the government, but because their backbench MPs number only 35, even if all of them vote against the government with all the opposition MPs, that is still not be enough to defeat the Government.

In practice, for the government's majority to fall much below 50, both Conservative and Liberal Democrats need to rebel in decent numbers, with the support of the Labour frontbench and the minor parties. This has so far happened on only 22 occasions in the coalition's first 24 months in power. But expect that number to rise over the next few months.

Philip Cowley is Professor of Parliamentary Government at the University of Nottingham. The Bumper Book of Coalition Rebellions by Philip Cowley and Mark Stuart is available to download here.