Returns statistical summary for a labor category: count, min, max, avg,
median, standard deviation, percentile distribution (P10-P90), education
breakdown, worksite counts (worksite_breakdown: Customer_Facility /
Contractor_Facility / Virtual; counts only, prices are pooled across
sites), and outlier bounds.

GSA's keyword search matches labor_category, vendor_name and idv_piid.
The returned statistics pool all matching rate rows, including unrelated
labor titles when a vendor name or contract number matches the phrase.
Check population_scope and matched_titles before using the statistics.
off_title_matches_detected flags observed titles that do not match the
requested phrase; title_only_population_verified is false when the title
aggregation is missing, empty, truncated or approximate.
A title containing the phrase is not necessarily the exact grade:
'Registered Nurse I' also matches Nurse II, III and IV. Check
exact_title_population_verified, exact_title_rate_count and
non_exact_title_examples before treating a pool as that specific title.

For title-only rates, call suggest_contains on labor_category to discover
an exact title, then exact_search on labor_category. Different spellings
remain separate searches ('Cyber Security Analyst' vs 'Cybersecurity
Analyst'). Statistics are on current-year ceiling rates (current_price),
not next-year or option-year prices.

These are not-to-exceed ceiling rates, not prices paid. Ceiling-rate
comparisons alone do not establish a proposed price's reasonableness.

Optional filters: education_level, experience_min/max, business_size
('S' or 'O'), sin (e.g. '541611'), security_clearance ('yes' or 'no').