Drop-off in speed as distance increases

If you compare your best times for the various events of a stroke, where does the biggest drop-off occure? Is this different for a sprinter compared to a swimmer of a distance persuasion? I noticed that there was little difference between my speed for the 800 free compared with my best 1500. In fact, my two best 800s are splits from my best 1500s. So I decided to take a closer look: Freestyle Masters PB, SCM: 50: 26.87 (100 m= 53.74) 100: 58.06 (58.06), drop-off=8.0 % 200: 2:05.61 (1:02.81), drop-off 8.2 % 400: 4:27.56 (1:06.89) drop-off 6.5 % 800: 9:19.13 (1:09.89) drop-off 4.5 % 1500: 17:31.38 (1:10.09) drop-off 0.3 % How would you analyze this? I would think that my 200 is sub standard (biggest drop-off), and so is my 800 (no faster than 1500). There's a lot of variables, of course; was I shaved and tapered for all these swims, what kind of suit did I wear, was it early or late in the meet etc. For the shorter swims, the drop-off is more substancial than for the longer swims. Is this due to my slow-twitch dominance or is it general? Could it have something to do with the different energy systems? Freestyle with all its events was the most interesting subject, but of course I checked the other strokes too. Not all to my surprise there was a discrepancy between butterfly and backstroke drop-offs, from 100 to 200 my speed dropped by 2.6 % (backstroke :)) and 18.0 % (butterfly :afraid:).