The dropout rate of entrants, qualifiers, and starters is a testament to the rigorous challenges presented by the Le Mans 24-hour race and sometimes in just getting there.

From the registered entrants who did not arrive, or arrived, but just too late to get on the grid (DNA) and the casualties in practice which prevented them from starting on race day (DNS) cars that were simply not accepted (NAC) and once the race started you could be black flagged (DISQ) for things like “illegal refuel”, “last lap over 30 minutes”, “outside assistance” , “refuelling too early”, and refuelling brake fluid".

For entrants that did not finish (DNF) the causes ranged from every aspect of mechanical failure, generally, the core reason was logged (brevity) and included everything from Engine (piston), connecting rod, gearbox/transmission, clutch, steering, oil pressure, ran out of water, ignition, suspension, brakes, rear axle and much more sobering reasons such as “falling asleep - accident” and in 1956 "Accident, collision with a dog".Inevitably there were too many occasions marked as “*Fatal accident”. 

Below lists the race year, entrants/teams who actually started the race, those that finished, also shown as a % of starters, and the race edition since 1923. I threw in 1931 at random with 23% of a much smaller field finishing the race. In 1923 some of the roads consisted of wooden planks.

Year   Strt    Fin  

1931    26    6    23%    9th Race
               
1949    49    19    39%    17th Race
1950    60    29    48%    18th Race
1951    60    30    50%    19th Race
1952    57    17    30%    20th Race
1953    60    26    43%    21th Race
1954    57    18    32%    22nd Race
1955    60    21    35%    23rd Race - The Le Mans Disaster
1956    49    14    29%    24th Race
1957    54    21    39%    25th Race
1958    55    20    36%    26th Race
Total    561  215  38%                
 

The fastest lap speed in 1931 was 125.735 km/h (78.128 mph) - Mercedes-Benz SSK

In 1937 155.179 km/h (96.423 mph) in a Bugatti 57 G

In 1950 165.49 km/h (102.830 mph) in a Talbot Lago T26 GS

In 1958 it was 202.015 km/h (125.526 mph) - Ferrari 335 S

In 1967 it was 237.971 km/h (147.86 mph) in a Ford GT Mk IV

In 1971 it was 244.387 km/h (152.134 mph) by a Porsche 917

In 2023 it was 236.7 km/h (147.078 mph) in a Ferrari 499P 

There have been various changes to the circuit throughout the years that have impacted the length of the course from the creation of a slip road onto the public roads that are used during the race and new corners added.

The catastrophic disaster during the race at Le Mans where 83 spectators and a driver were killed and 120 injured was a major factor in shaping attitudes to safety in an inherently dangerous sport for both spectators and participants and course changes for the following year 

Engine size restrictions and chicanes, installed all contribute to restrictions in speed, but somehow records keep getting broken at Le Mans!

One thing is certain, that manufacturers who successfully race cars at Le Mans and not just hypercars, but those that can be be bought by the public without onerous modifications are always going to keep the brand in the public eye.

Luigi Chinetti recognised and proved that establishing a vehicles provenance at the toughest endurance race in the world in his first outing in a Ferrari in 1949 was good business as he then became the exclusive American importer of Ferrari automobiles to the United States.

William Reynolds followed suit in the 50's for Jaguar as would Henry Ford II, who initially tried to buy Ferrari to reverse the flagging fortunes of Ford in the 60's before establishing his own competition team.