If you want to know how well the NHS is coping with demand, you could do worse than to look at the performance of A&E departments.
At this week's Prime Minister's Questions, David Cameron once again defended his government's record in this regard, insisting that "last week was the 27th week in a row that we met our A&E targets".
In reply Ed Miliband said, "The Prime Minister is simply wrong about the figures. If we look at what is happening in our hospital A&E departments, we see that the target has been missed for 15 consecutive weeks".
Depending upon how you slice the weekly A&E data, they are in fact both correct. However - something that's not obvious from the exchange - Mr Miliband's figures are more specific.
A&E departments are supposed to see 95% of patients within four hours. According to the latest figures, on average England's A&E departments have met this government target every week since the end of April, as the Prime Minister claimed.
Meanwhile, Ed Miliband has chosen to look solely at major A&Es. These so-called Type 1 units are 'consultant-led' and open 24 hours a day. Since the beginning of July, on average Type 1 units have failed to see 95% of patients within the four hour target. By focusing on Type 1 departments, Mr Miliband doesn't include what's happened to waiting times at other A&E departments - both Type 2 units (smaller, single specialty departments) and Type 3 units (walk-in centres for minor injuries).
Mr Cameron is referring to all A&Es, whereas Mr Miliband is focusing on the biggest departments. It's arguable whose measure is the most useful - the Prime Minister looks at the situation in the round while the leader of the Opposition hones in on where the problem is concentrated (although on this occasion doesn't make this particularly clear).
While the government has dismissed Labour's talk of a "crisis", it knows that the coming months are likely to be particularly busy for A&E departments. There's usually a spike in A&E waiting times during the winter - the period when departments of every shape and size are most at risk of missing their targets. Perhaps to ease the pressure, the Coalition recently announced that over the next two years it would provide A&E departments with an extra £500 million.