Bicycles with vertical dropouts and no derailleur require some way to adjust chain tension. Around 60 percent of black dropouts end up spending time incarcerated. Of these students, 25% are chronic procrastinators and typically abandon higher education (college dropouts). High-school dropouts fared worse with negative growth. Frames with horizontal dropouts are straightforward to convert, frames with vertical dropouts less so. The axle is attached to dropouts on the fork or the frame. The percentage of students who were event dropouts decreased from 1972 through 1987. Statistics show that the majority of dropouts are below the poverty line. Rear "vertical dropouts" have the slot facing downwards. The most common method is horizontal rear dropouts or track ends. In the United States, 75 percent of crimes are committed by high school dropouts. The county has about twice the state average in terms of high school dropouts. They may be subject to dropouts caused by interference from other devices. Bicycles with vertical dropouts can also be converted with some additional hardware. There were issues with sound quality due to dropouts in the audio.