Thinking about it a bit more - it probably depends on how you describe what is being measured. Along a given line of longitude - measuring 1 degree of arc - is equivalent to measuring between X degrees latitude and (X+1) degrees latitude. Hence - it is the difference between degrees of latitude (providing longitude is constant.).

I was thinking the answer was implying measurement along a constant degree of latitude, e.g. from Y degrees longitude to Y+1 degrees longitude which does get smaller approaching the poles.

:hehe: