Answer: Social Security only looks at your “past relevant work” in considering your case. The SSA defines Past Relevant Work as “work that you have done within the past 15 years, that was substantial gainful activity, and that lasted long enough for you to learn to do it.” (See http://www.ssa.gov/OP_Home/cfr20/416/416-0960.htm).
Work Done In The Past 15 Years
Most ALJs interpret this to mean 15 years before the date of the hearing. So, if your hearing is in 2013, the Judge will look at work that you have done going back to 1998. There is an exception to this for cases involving a remote date last insured (DLI). (For more on understanding your date last insured, see this post). Basically, in these instances, the ALJ may look back to work done 15 years before your DLI expired.
The Work Activity Was Substantially Gainful (SGA)
The SSA usually applies a simple earnings test to determine whether work activity is SGA. For 2012, SGA is set at $1,010 a month. For 2013, the rate goes up to 1,040 a month.
Example: If you performed a job on a part-time basis in 2012 and earned gross earnings of $600.00 a month, these positions would probably not be considered as past relevant work.
For more on SGA, see this previous post on Step 1 of the Sequential Evaluation Process.
The Job Lasted Long Enough To Learn It
Some jobs require more skill and training than others. Unskilled jobs may be learned in a matter of days, whereas skilled positions may take years to master. Generally, the SSA is only supposed to consider jobs that you have mastered. This will mean that some skilled positions (e.g. nurse, carpenter, etc.) may not be found to be relevant after performing it for a year, but an unskilled job (e.g. small parts assembler, grocery store stocker, etc.) may be considered after you doing the job for only a month.