Use reliable data of the same period of time. You can find figures on an economy's total expenditure on the CIA World Factbook, defense costs at the annual SIPRI Yearbook and figures on health expenditure per capita at the World Bank's website for example.
Convert all figures to a single currency. This is an especially important step when you have accumulated data from national statistics bureaus. For example, the U.S. Census Bureau's data are in U.S. dollars, while the website of the U.K. National Statistics offers figures in British pounds.
Give information on the country's or community's population, nominal expenditure on a certain sector. This way, you help readers judge by themselves if a country's or community's spending is justified by its size. For example, California legislature's operating costs for fiscal year 2010 were approximately $342 million, but since it's serving nearly 40 million people, the per capita cost is $8.55; on the contrary, Connecticut legislature costs the state's 3.5 million residents approximately $70 or $20 per capita.
Clarify differences on how each community or country measures its per capita expenditure. For instance, according to professor Sandra Hopkins, long-term care in some countries can be provided by hospitals, in some by residential care and in others at home. This can render different data difficult to compare directly.
Provide the GDP per capita figures to show the connection between the approximate figures of a person's finances and governmental or private sector expenditure. For example, the U.S. GDP per capita (per purchasing parity) is $47,200 as of 2010, according to the CIA World Factbook. Military spending per capita for the same year (according to SIPRI Yearbook 2010) was $2,100 or 4.4 percent of GDP per capita.