Forty-three of the 499 listings on the S&P 500’s launch-day roster of 4 March 1957 are still in the index without ever having been removed, and 15 of them now trade under a different ticker. Across the whole record, which opens with the index’s predecessor at the end of 1925, 1,972 listed securities have been S&P 500 members; today’s 503 are about a quarter of them.
How many companies have ever been in the S&P 500?
The published answers are old. When the index turned 50, S&P said that 86 of its original constituents had survived (PLANSPONSOR, 2 March 2007). A Reuters timeline of 10 April 2013 put the figure at 69 of the 500 original companies. Neither gives a total for the companies that have passed through the index, nor says how a merged or renamed company was counted.
Today’s member list cannot answer the question: companies that were acquired, failed or were demoted leave no trace in it, the mechanism behind survivorship bias in backtesting.
The unit counted here is the listed security (one share class). Alphabet, with two classes in the index, counts twice. A reorganisation that created a new listed security counts as a new listing: Union Pacific Railroad had its last day in the index on 15 July 1969 and Union Pacific Corporation joined on 16 July. A count that follows company lineage would merge such pairs, giving fewer companies in total and more surviving originals.
Counting listings from the event log and two rosters
- Page through the full event log with
index_events: 3,612 dated additions and removals; the guide to S&P 500 additions and deletions history explains the log. Founding members carry no addition row, so the opening roster of 31 December 1925 comes fromas_of. - Count distinct listings by
entity_id, which stays with a security through renames and ticker changes (by ticker where a row has none). - Take the launch-day roster with
as_of="1957-03-04": 499 listings. Each row’sremoved_datecloses the membership open that day, so rows with a blankremoved_date, or one on or after the date checked, are the listings still in without a break. - Join that roster to today’s on
entity_id; a current membership that began after 4 March 1957 marks a listing removed and later re-added. - Repeat the counts on the dates of the two published figures.
Code
import xfinlink as xfl
import pandas as pd
xfl.set_api_key("YOUR_API_KEY") # free at https://xfinlink.com/signup
LAUNCH = "1957-03-04" # first day of the 500-stock index
def all_events():
pages = [xfl.index_events("sp500", start="1925-12-31")]
while len(pages[-1]) == 1000: # one call returns at most 1,000 rows
pages.append(xfl.index_events("sp500", start="1925-12-31", offset=1000 * len(pages)))
return pd.concat(pages, ignore_index=True)
def listings(df): # one key per listed security: entity_id, or ticker where no id is linked
linked = set(df["entity_id"].dropna().astype(int))
return linked | set("ticker " + df.loc[df["entity_id"].isna(), "ticker"])
ev = all_events()
opening = xfl.index("sp500", as_of="1925-12-31") # the opening roster has no addition rows
launch = xfl.index("sp500", as_of=LAUNCH)
today = xfl.index("sp500")
ever = listings(ev) | listings(opening)
since_launch = listings(ev[ev["effective_date"] >= LAUNCH]) | listings(launch)
# removed_date ends the membership that was open on launch day
launch["last_day"] = launch["removed_date"].fillna("9999-12-31")
unbroken = pd.Series({y: int((launch["last_day"] >= f"{y}-03-04").sum()) for y in range(1957, 2027)})
now = launch.merge(today[["entity_id", "ticker", "added_date"]], on="entity_id", suffixes=("_1957", "_now"))
stayed = now[now["added_date_now"] <= LAUNCH] # current membership began on or before launch
print(len(ever), len(since_launch), len(today), len(launch), len(now), len(stayed),
(stayed["ticker_1957"] != stayed["ticker_now"]).sum())
print(unbroken[[1967, 1977, 1987, 1997, 2007, 2017, 2026]].to_dict())
for day in ("2007-03-02", "2013-04-10"): # dates of the S&P and Reuters counts
on_day = set(xfl.index("sp500", as_of=day)["entity_id"].dropna())
print(day, (launch["last_day"] >= day).sum(), len(on_day & set(launch["entity_id"])))
print(today["added_date"].str[:3].add("0s").value_counts().sort_index().to_dict())Full script with formatting and visualisation: sp500-members-1957-originals-python.py
Output
S&P 500 event log: 3,612 rows, 1928-08-24 to 2026-10-06
Listings ever in the index (record opens 1925-12-31): 1,972
Listings in the index on or after 1957-03-04: 1,944
Members today: 503 (25.5% of all listings ever)
Launch-day roster (1957-03-04): 499 listings
in today's roster: 53
of which never left: 43
removed and later re-added: 10
never-left listings on a new ticker: 15
Launch-day listings still in without a break, on 4 March of:
1967: 380
1977: 247
1987: 168
1997: 126
2007: 69
2017: 51
2026: 44
today: 43
left since 4 March 2026: CPB (CAMPBELLS CO, last day 2026-06-18)
first 4 March below half the roster: 1977
largest one-day exit: 21 on 1976-06-30 (46 removals that day, 46 additions on 1976-07-01)
On 2007-03-02: never left 69, in the index (re-additions counted) 76
On 2013-04-10: never left 55, in the index (re-additions counted) 65
Today's members by decade their current membership began:
decade
1920s 7
1940s 4
1950s 34
1960s 9
1970s 21
1980s 46
1990s 60
2000s 88
2010s 133
2020s 101
Never left since 1957, ticker then -> now (earliest current membership first):
SD -> CVX CHEVRON CORP NEW since 1925-12-31 (new ticker)
DTE -> DTE D T E ENERGY CO since 1925-12-31
ED -> ED CONSOLIDATED EDISON INC since 1925-12-31
SCE -> EIX EDISON INTERNATIONAL since 1925-12-31 (new ticker)
ACD -> HON HONEYWELL INTERNATIONAL INC since 1925-12-31 (new ticker)
IP -> IP INTERNATIONAL PAPER CO since 1925-12-31
J -> XOM EXXON MOBIL CORP since 1925-12-31 (new ticker)
PE -> EXC EXELON CORP since 1944-06-07 (new ticker)
SO -> SO SOUTHERN CO since 1944-06-07
PEG -> PEG PUBLIC SERVICE ENTERPRISE GP INC since 1948-07-07
NSP -> XEL X C E L ENERGY INC since 1949-07-06 (new ticker)
AEP -> AEP AMERICAN ELECTRIC POWER CO INC since 1951-09-06
ABT -> ABT ABBOTT LABORATORIES since 1957-03-01
BA -> BA BOEING CO since 1957-03-01
BMY -> BMY BRISTOL MYERS SQUIBB CO since 1957-03-01
CTR -> CAT CATERPILLAR INC since 1957-03-01 (new ticker)
CL -> CL COLGATE PALMOLIVE CO since 1957-03-01
P -> COP CONOCOPHILLIPS since 1957-03-01 (new ticker)
MES -> CVS C V S HEALTH CORP since 1957-03-01 (new ticker)
DE -> DE DEERE & CO since 1957-03-01
ENX -> ETN EATON CORP PLC since 1957-03-01 (new ticker)
MSU -> ETR ENTERGY CORP NEW since 1957-03-01 (new ticker)
F -> F FORD MOTOR CO DEL since 1957-03-01
GD -> GD GENERAL DYNAMICS CORP since 1957-03-01
GE -> GE GENERAL ELECTRIC CO since 1957-03-01
GLW -> GLW CORNING INC since 1957-03-01
HAL -> HAL HALLIBURTON CO since 1957-03-01
HSY -> HSY HERSHEY CO since 1957-03-01
AA -> HWM HOWMET AEROSPACE INC since 1957-03-01 (new ticker)
IBM -> IBM INTERNATIONAL BUSINESS MACHS COR since 1957-03-01
KMB -> KMB KIMBERLY CLARK CORP since 1957-03-01
KO -> KO COCA COLA CO since 1957-03-01
KR -> KR KROGER CO since 1957-03-01
MMM -> MMM 3M CO since 1957-03-01
MO -> MO ALTRIA GROUP INC since 1957-03-01
MRK -> MRK MERCK & CO INC NEW since 1957-03-01
MOT -> MSI MOTOROLA SOLUTIONS INC since 1957-03-01 (new ticker)
PEP -> PEP PEPSICO INC since 1957-03-01
PFE -> PFE PFIZER INC since 1957-03-01
PG -> PG PROCTER & GAMBLE CO since 1957-03-01
PPG -> PPG P P G INDUSTRIES INC since 1957-03-01
UA -> RTX R T X CORP since 1957-03-01 (new ticker)
MHP -> SPGI S & P GLOBAL INC since 1957-03-01 (new ticker)
Re-added after leaving:
SLB -> SLB SLB LTD back since 1965-03-04
GIS -> GIS GENERAL MILLS INC back since 1969-02-13
ADM -> ADM ARCHER DANIELS MIDLAND CO back since 1981-07-30
LK -> LMT LOCKHEED MARTIN CORP back since 1984-07-19
CMS -> CMS C M S ENERGY CORP back since 1999-05-03
HI -> LHX L3HARRIS TECHNOLOGIES INC back since 2008-09-22
ONG -> OKE ONEOK INC NEW back since 2010-03-15
IR -> TT TRANE TECHNOLOGIES PLC back since 2010-11-17
EQT -> EQT E Q T CORP back since 2022-10-03
PCG -> PCG P G & E CORP back since 2022-10-03Why 43 is lower than the published counts
The roster thinned fastest early: 380 of the 499 were still in by March 1967 and 247, below half, by March 1977. The largest single exit came on 30 June 1976, when 21 launch-day listings left in a change that swapped 46 members. Between 2017 and 2026 only seven more left, and the 44th, Campbell’s, had its last day on 18 June 2026.
Neither source states its unit, so the gap most likely reflects definition rather than a different history. On 2 March 2007, 69 launch-day listings had never left and 76 were in the index when re-additions count, against S&P’s 86. On 10 April 2013 the same counts are 55 and 65, against Reuters’ 69. A count that follows company lineage would treat a successor as the original carrying on, as with Union Pacific in 1969; a listing count does not.
Ticker changes are a separate trap. Fifteen of the 43 trade under a new symbol: Standard Oil Company (New Jersey), listed as J, is now Exxon Mobil (XOM); Melville Shoe’s MES is CVS Health. Matching the 1957 roster to today’s tickers would record all fifteen as departures. The ten re-added listings, Schlumberger (now SLB) and Lockheed (now Lockheed Martin) among them, are members today but not unbroken ones.
Today’s index is young: 234 of its 503 members began their current membership in 2010 or later, and 45 in the 1950s or earlier. Membership length across every cohort of entrants is the subject of a Kaplan-Meier survival analysis of S&P 500 membership.
Starting a 1957 universe without losing renamed members
A backtest or longevity study that begins in 1957 should start from the 499 listings on the launch-day roster, not from today’s members filtered by join date, and key them by a persistent identifier rather than ticker or name. Keyed by entity_id, the fifteen renamed survivors keep their history and the listings that left stay in the sample until their last day.
A count of original members should state its unit, listed security or company lineage, unbroken or on the date; on one day in March 2007 the two listing counts give 69 and 76, against S&P’s published 86.
Past rosters come from as_of on the index membership endpoint, and the S&P 500 members on any date since 1925 can be looked up without code.
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