Why Can’t I Start a Sentence With a Numeral?

Here’s a sentence for you to ponder:

1968 was no year for a catching of the breath.

This is a no-no, because you’re not supposed to start a sentence with a numeral. Because of this rule, here’s how that sentence is rendered in Todd Gitlin’s The Sixties:

Nineteen sixty-eight was no year for a catching of the breath.

That sure looks dumb to me. But hey, rules are rules. Whatcha gonna do? I say: change the rule. For one thing, I don’t know where this “rule” came from. Who invented it? Why do we follow it? For example, what’s wrong with the following sentence, which is a pretty common formulation?

69 percent of Americans believe the earth is getting warmer due to human activity. That drops to 23 percent among Republicans.

That seems perfectly readable to me, whereas spelling out sixty-nine doesn’t. That’s because we’re not used to seeing large numbers spelled out, since it’s never done anywhere else. Note that if we abolished this rule it would also solve the idiotic workaround of things like, “Seven in ten Americans believe the earth is getting warmer.” That solves the copy-editing problem, but makes the entire story hard to read and less accurate. Writers end up switching back and forth between percentages and fractions, which is confusing as hell.

Please note that none of this applies to small numbers, which have their own rule: numbers from 0-12 are generally spelled out, while larger numbers are rendered in numerals. So you’d never see, for example, “3 of my friends are coming over to visit.”

Change the rule! Change the rule! Who do I see about doing this?