Table 2 All dyadic juxtapositions of the six measures of demographic time

Variants of APC

AP(C) C = P − A

The AP(C) temporal plane constitutes the classical Lexis diagram.

AC(P) P = C + A

The AC(P) temporal plane is equivalent to the Lexis diagram except birth cohort is given and period is derived rather than the other way around.

CP(A) A = P − C

The CP(A) temporal plane is equivalent to the Lexis diagram except birth cohorts are given and age is derived rather than the other way around.

Variants of TPD

TP(D) D = P + T

Helen had 30 years of life left (T) in 1971 (P) and therefore belonged to the 2001 death cohort (D)

PD(T) T = D − P

Mindel died in 1973 (D). In 1953 (P) she had 20 years left to live (T).

TD(P) P = D − T

Irene died in 1974 (D). When she had 30 remaining years of life (T) the year must have been 1944 (P).

Variants of TAL

TA(L) L = T + A

The time already lived and the time still left sum up to the total lifespan.

TL(A) A = L − T

Helen lived to the age of 86 (L). When she had 20 years left (T) she must have been 66 (A).

AL(T) T = A − L

Tim is 34 years old (A) and will live to the age of 96 (L), leaving him 62 years (T) to settle affairs.

Variants of LCD

LC(D) D = C + L

Àngels was born in 1940 (C) and she lived to be 64 (L), implying an untimely death in 2004 (D)

CD(L) L = D − C

Pascal was born in 1893 (C) and died in 1964 (D), implying a lifespan of 71 (L), or so.

LD(C) C = D − L

Margaret died in Dec., 1995 (D) with a completed lifespan of 96 (L), putting her birth year in 1900 (C).

The uninformative dyads

LP(-)

The LP plane is non-informative. No additional measures can be derived knowing just lifespan and period.

CT(-)

The CT plane is non-informative. No additional measures can be derived knowing just birth cohort and thanatological age.

AD(-)

The AD plane is non-informative. No additional measures can be derived knowing just death cohort and age.