Adjust Per-capita

adjustpc(VALUEFORYEAR1,YEAR1,YEAR2) adjusts the number VALUEFORYEAR1 from what it was in YEAR1 to what it was in YEAR2. The adjustment is per capita, based on historical population data previously obtained from the U.S. Census Bureau.

VALUEFORYEAR1 can be any number. YEAR1 and YEAR2 each can both be any year from 1900 to the current year. YEAR2 is optional, with its default value being the current year.

The input arguments can either be single numbers, or row or column vectors of the same size.

Population data is read from the the data file. It is assumed that the file contains data for both YEAR1 and YEAR2. This file can be updated
using a text editor - if and when this needs to be done. Microsoft Excel should not be used to do this, as it can alter the date format. The
updated file must contain data for all years up to the current year.

EXAMPLES:

adjustpc(1,1900,2007) returns 3.9542
Because in this case ValueForYear1 equals 1, this indicates that the population in 2007 was 3.9542 times that in 1900.

adjustpc(1,1900) also returns 3.9542
adjustpc(1,2007,1900) returns 0.2529

adjustpc(10,1945,1960) returns 12.9117
This indicates that 10 units of something (e.g. dollars) for the entire population in 1945 would correspond to having 12.9117 units of that thing for the entire population in 1960.

ValueForYear1=[4 1 15];
Year1=[1920 1973 2002];
Year2=repmat(2005,size(Year1));
adjustpc(ValueForYear1,Year1,Year2) returns [11.1405 1.3992 15.4363]

REMARKS:

For efficiency, population data is read from the data file into RAM only once per session, after which it stays in RAM for the remainder of
the session. For more implementation details, see the relevant PopForYear subfunction section of the code.

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