By law certain retirement plan limits get adjusted every year, not exactly tracking inflation (i.e., not by the CPI) but rather in “chunks” which approximate it.

For 2015, the following limits have been announced:

IRA Contributions (combined limit across Roth and Traditional): $5,500
IRA Catch-Up Contributions (for folks over 50): $1000
[Both unchanged from 2014 and, actually, 2013]

Start of Phaseout of tax-deduction for traditional IRA contributions:
Joint Return: $98,000  (up from $96,000 in 2014)
Single: $61,000 (up from $60,000 in 2014)

SEP (Simplified Employee Pensions – often used as SEP-IRAs for self-employed):
SEP Minimum Compensation: $600 (up from $550 in 2014)
SEP Maximum Contribution: $53,000 (up from $52,000 in 2014)
SEP Maximum Compensation: $265,000 (up from $260,000 in 2014) 

SIMPLE Maximum Contribution: $12,500 (up from $12,000 in 2014)
SIMPLE Catch-Up Contribution: $3,000 (up from $2,500 in 2014)

401(k) Annual Compensation: $265,000 (up from $260,000) — maximum income on which 401(k) contributions are based
401(k) Elective Deferrals: $18,000 (up from $17,500 in 2014) — maximum EMPLOYEE contribution
401(k) Catch-Up Contribution: $6,000 (up from $5,500 in 2014) — for folks over 50
Defined Contribution Limit: $53,000 (up from $52,000) — maximum combined EMPLOYER PLUS EMPLOYEE (not incl. catch-up)

Social Security Taxable Wage Base: $118,500 (up from $117,000) — this is the amount of earned income on which Social Security taxes are collected.  Any income above that is still subject to Medicare taxes.

Source: http://www.irs.gov/Retirement-Plans/COLA-Increases-for-Dollar-Limitations-on-Benefits-and-Contributions