16.11 Toxic releases. The Environmental Protection Agency requires industry to report releases of any of a list of toxic chemicals. The total amounts released (in thousands of pounds, total on- and offsite disposal or other releases, all chemicals, all industries) were 6,939,299 in 1988, 6,655,831 in 2000, and 4,137,328 in 2013. Give an index number for toxic chemical releases in each of these years, with 1988 as the base period. By what percentage did releases increase or decrease between 1988 and 2000? Between 1988 and 2013?