Hydrostatic gauges (such as the mercury column manometer) consist of a vertical column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. The simplest design is a closed-end U-shaped tube, one side of which is connected to the region of interest. Any fluid can be used, but mercury is preferred for its high density and low vapour pressure. Simple hydrostatic gauges can measure pressures ranging from 1 torr (100 Pa) to above atmospheric. An important variation is the McLeod gauge which isolates a known volume of vacuum and compresses it to multiply the height variation of the liquid column. The McLeod gauge can measure vacuums as high as 106 torr (0.1 mPa), which is the lowest direct measurement of pressure that is possible with current technology. Other vacuum gauges can measure lower pressures, but only indirectly by measurement of other pressure-controlled properties. These indirect measurements must be calibrated via a direct measurement, most commonly a McLeod gauge.
What is a vertical column of liquid in a tube which has different pressures at each end called?
Hydrostatic gauges

In the city the population was spread out with 25.7% under the age of 18, 8.9% from 18 to 24, 31.0% from 25 to 44, 20.2% from 45 to 64, and 14.2% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 96.1 males. For every 100 females age 18 and over, there were 93.2 males.
What percentage of the population of Atlantic City was 65 years of age or older?
14.2%

FBI records show that 85% of COINTELPRO resources targeted groups and individuals that the FBI deemed "subversive", including communist and socialist organizations; organizations and individuals associated with the Civil Rights Movement, including Martin Luther King, Jr. and others associated with the Southern Christian Leadership Conference, the National Association for the Advancement of Colored People, and the Congress of Racial Equality and other civil rights organizations; black nationalist groups; the American Indian Movement; a broad range of organizations labeled "New Left", including Students for a Democratic Society and the Weathermen; almost all groups protesting the Vietnam War, as well as individual student demonstrators with no group affiliation; the National Lawyers Guild; organizations and individuals associated with the women's rights movement; nationalist groups such as those seeking independence for Puerto Rico, United Ireland, and Cuban exile movements including Orlando Bosch's Cuban Power and the Cuban Nationalist Movement. The remaining 15% of COINTELPRO resources were expended to marginalize and subvert white hate groups, including the Ku Klux Klan and the National States' Rights Party.
What percentage of COINTELPRO resources were targeted at FBI labeled subversive groups?
85%