In theory, yes. But in practice, most miners have joined a mining pool. Mining pools allow miners to share in the rewards, which means they have a vastly more predictable income per block. A solo miner would probably not have a statistically significant chance of finding a single block for the next 100 years, while pooled miners earn bitcoin through finding blocks roughly equivalent to the mining pools relative size compared with the total hash rate. Since mining is a cutthroat, bleeding edge, hypercompetitive system, that means dependability and stability are very important.