"half as successful" is correct and usable in written English.
You can use this phrase when you want to express that something is not as successful or not as far-reaching as something else. For example: "Although the marketing campaign was successful, it was only half as successful as the one from the previous year."
Second, the exposed bees are half as successful in gathering food.
He says if 2018 is half as successful, he'll be happy.
If Abenomics is even half as successful as its advocates hope, it will have still more to teach us.
Those figures suggest the genetically engineered males were about half as successful in mating as wild ones, a rate sufficient to suppress the population.
Most YouTubers who are even half as successful as Zoella will have more creative freedom – and be earning more money – on YouTube".
If Lucky Jim is half as successful as Varenne on the track then he need never worry about having to travel with his own hay and grain again.
Although their training is almost as lengthy and intense as that of medical doctors, few veterinarians can expect to be even half as financially successful, according to the American Animal Hospital Assn., the national certifying organization based in Lakewood, Colo.
Aetna told the analysts it expected profits of $1.20 to $1.30 a share next year, and its profit margins are only half as large as those of successful competitors like the Cigna Corporation, the United Health Group and Wellpoint Health Networks.
And the complaints about Mr Norquist would not be half as loud if he were not so successful.
If Haslett had allowed herself to absorb Weil's idea of attention in its fullness, the second half of her film would have been as successful as the first half.
And those they selected were half as likely to appear in newspaper articles as the bosses of less successful companies.
