APES formulas

Population density

Population density = population/ area

Growth rate %

Growth rate = (births-deaths/ total population) x 100

Doubling time (rule of 70)

Number of years to double = 70/ annual % growth rate

Crude birth/ death rate

Births/ deaths/ total population x 100

Crude growth rate

CBR-CDR/ 10

Per capita

Population measurement / population size

Net population change

(Births + immigration) - (deaths - emigration)

Percent change

% increase = new - initial value/ initial value x 100

Rate of change

final value- initial value/ final year - initial year

Half life

Amount remaining = (original amount) x (0.5^x

(x = # of half lives)

Total energy used

kWx hours = kWh

Energy efficiency

Efficiency of step 1 x efficiency of step 2, etc. x 100

Primary productivity

NPP = GPP - R